population| types| function| definition| structure| curve| commensalism| mutualism| Amensalism|

Population

It can be defined as the total number of individuals of a species in a specific geographical area, which can interbreed under natural conditions to produce fertile offspring and function as a unit of biotic community. 

Population Ecology 

It is an important area of ecology as it links ecology to the population genetics and evolution.

Population Attributes 

These are certain characteristics of a population. Some of them are as follows:

Population Size or Density 

It is the number of individuals of a species per unit area or volume at a given time.

Population Density: -

Death Rate or Mortality 

• It is expressed as the number of deaths per 1000 individuals of a population per year, e.g. if 4 individuals in a population of 40 fruit flies died during a specified time interval (say a week). 
• Death rate= 4/40 = 0.1 (individual per fruit fly per week)

Sex Ratio 

• It is expressed as the number of females and males per 1000 individuals of a population in a given time, e.g., 60% females and 40% males in population. 

Age Pyramid 

1. When the age distribution (per cent individuals of a given age or age group) is plotted for the population in which. pre-reproductive age is at base, reproductive is in middle and post-reproductive is at top, we get a pyramid called age pyramid.
2. The shape of the pyramids reflects the growth status of the population that whether it is expanding (triangular-shaped), stable (bell-shaped) or declining (Urn-shaped).

   

   Fig: - Representation of age pyramids for human population
   
   
   

Population Growth: -

• The size of a population for any species is   not a static parameter. 
• It keeps changing with time, depending on various factors including food availability, predation, pressure and adverse weather conditions.
• The density of a population in a given habitat during a given period fluctuates due to changes in four basic processes:

(a) Natality is the number of births during a given period in the population that are added to the initial density.

(b) Mortality is the number of deaths in the population during a given period.

(c) Immigration is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration. 

(d) Emigration is the number of individuals of the population who left the habitat and  moved elsewhere during a given time Period. 

Figure: -Factors influencing population density

Note: - Natality and immigration contribute to an increase in population density and mortality and emigration contributes to a decrease.

• Population density can be given by the following equation 

          N1+1 = N1 + [(B + I) - (D + E)] this is density at time t + 1.

Where, N = population density, t = Time,

       B = Birth rate,I = Immigration, D = Death rate, E = Emmigration, N1 = Population in beginning.

The equation demonstrates that the population density will increase, if the number of births plus the number of immigrants (B + I) is more than the number of deaths plus the number of emigrants (D + E), otherwise it will decrease. 

• Although total number is the most appropriate measure of population density. In some cases, it is difficult to determine. So, in these cases, the per cent cover or biomass is a more appropriate measure of the population size, e.g. 200 Parthenium plants and a single huge banyan tree. In this case, the banyan tree produces much more biomass. 
• Total number is not an appropriate measure in case of huge population size. In such case, relative densities are used. For example, the number of fishes caught per trap is a good measure of its total population density in the lake. It is an indirect method to estimate population size.
• In some cases, population size is estimated indirectly. Without actually counting or seeing them, e.g. the tiger census is based on pug marks and faecal pellets.
• Growth curves of population are of the following types: -

(a) Exponential growth (A-curve) occurs normally when resources, i.e., food and space are unlimited. 

• Equation for exponential growth can be represented as follows: -

dN/dt = (b-d) N

let (b-d) = r, then 

dN/dt = rN

Where,

N = Population size,

Nt = Population density after time t

N.= Population density at time zero, 

r = Intrinsic rate of natural increase

e = Base of natural logarithms (2.71828), 

b = Birth rate and 

d = Death rate

Fig: - Population growth curve, A- when responses are limiting the growth, plot is exponential,
B- when responses are limiting the growth, plot is logistic, K- is carrying capacity.

• r is an important parameter assessing impacts of any biotic or abiotic factor on population growth.
• In exponential growth, when N in relation to time (t) is plotted on graph, the curve becomes J-shaped as shown in graph. 

(b) Logistic growth (B-curve) occurs when resources become limited at certain point of time, so no population can grow exponentially. 

• Due to competition between individuals for limited resources, the fittest individual will survive and reproduce. 
• In nature, a given habitat has enough resources to support a maximum possible number, beyond which no further growth is possible. This is called carrying capacity (K) of a habitat.
• A population growing in a habitat with limited resources shows initially a lag phase, followed by phases of acceleration and deceleration and finally an asymptote, when the population density reaches the carrying capacity. 
• The logistic growth shows sigmoid curve and this is also called Verhulst-Pearl logistic growth. 
• The logistic growth model is considered more realistic since, resources for groWth of most animal populations are finite and become limited sooner or later.

Life History Variation 

(i) Darwinian fitness (high r value) states that the Populations evolve to maximize their reproductive fitness in the habitat in which they live. 

(ii) Under a particular set of selection pressures, organisn1s evolve towards the most efficient reproductive strategy.

(iii) The rate of breeding varies from species to species, e.g. Pacific salmon fish and bamboo breed only once in their lifetime, while most birds and mammals breed many times in their life.

(iv) Some organisms produce a large number of small-sized offspring (oysters, pelagic fishes), while birds and mammals produce a small number of large-sized offspring.

(v) Ecologists suggest that life history traits of organisms have evolved in relation to the constraints imposed by the abiotic and biotic components of the habitat in which they live.

Population Interactions

Population interactions explain that in nature, animals, plants and microbes cannot live in an isolation but interact in various ways to form a biological community.

(i) Interspecific interactions arise from the interaction of populations of two different species. 

(ii) This interaction may be 

(a) Beneficial/positive (+) 

(b) Detrimental/harmful (-) 

(c) Neutral (neither harm nor benefit) to one of the species or both (O) 

Population Interactions

Some of the population interactions are as follows: -

Predation: -

It is an interspecific interaction, where an animal called predator kills and consumes the other weaker animal called prey. This is a biological control method.

(i) It is the nature's way of transferring energy to higher trophic levels, which is fixed by plants, e.g. tiger eating a deer, sparrow eating seeds, etc. 

(ii) Important roles of predators are: - 

• They keep prey population under control. 
• They help in maintaining species diversity in a community by reducing the intensity of competition among prey species. For example, in American Pacific coast, the star fish Pisaster is an important predator. When all the fishes were removed from an area more than 10 species of invertebrates became extinct within a year due to in Ter specific competition.
• In the absence of predators, prey species could achieve very high population densities and cause instability. So, besides acting as 'conduits' for energy transfer across trophic levels, predators play very important role to provide population stability.

(iii)When certain exotic species are introduced into a geographical area, they become invasive and start spreading fast because the invaded land does not have natural predators, e.g. prickly pear cactus introduced in Australia (1920s) caused havoc by spreading rapidly over a large area. It was controlled only after a cactus feeding predator (a moth) was brought from its natural habitat. 

(iv) If a predator is too efficient and over exploits its prey, then the prey might become extinct. Following it, the predator will also become extinct because of the lack of food.

(v) Prey species have evolved various defense mechanisms to lesser the impact of predation. Some of them are: -

• Some species of insects and frogs are cryptically colored (camouflaged) to avoid being detected easily by the predator. Some are poisonous and therefore, avoided by the predator.
• Phytophagous insects like Monarch butterfly is highly distasteful to its. predators (birds) because of a special chemical present in its body. The . butterfly acquires this chemical dunng its caterpillar stage by f ceding on a poisonous plant (weed). 
• Some plants have thorns or spines fo r defence mechanism, e.g. Acacia, cactus. 
• Some plants produce highly poisonous chemicals like cardiac glycosides, nicotine, caffeine, quinine, strychnine, opium, etc. These are actually defence mechanisms against grazers and browsers. e.g. Calotropis. These chemicals make the herbivore sick when th ey are eaten, inhibit digestion, disrupt reproduction or even kill them.

Competition: -

It is a type of interaction, where both the species suffer. It occurs when species (closely related or even unrelated), compete for the same resources that are limited, e.g. in some shallow South American lakes visiting flamingoes and resident fishes compete for their common food, i.e. Zooplanktons. In other words, it can be defined as a process in which the fitness of one species (measured in terms of its 'r' the intrinsic rate of increase) is lower in the presence of another species. 

(i) It may be 

• Intraspecific (within same species). 
• Interspecific (between different species).

(ii) In interference/interspecific competition the feeding efficiency of one species might be reduced due to the interfering and inhibitory presence of other species, although the resources (food and space) are plenty. 

(iii) Competitive release is a phenomenon. in which a species whose distribution is restricted to a small geographical area because of the presence of competitively superior species, is found to expand its distributional range dramatically when the competing species is experimentally · removed. 

(iv) Connels' elegant field experiments showed that on the rocky seacoasts of Scotland, the larger and competitively superior barnacle Balanus dominates the intertidal area and excludes the smaller barnacle Chatha malus from that zone. 

(v) Gause's competitive exclusion principle states that two closely related species competing for the Sarne resources cannot coexist indefinitely and the competitively inferior one will be eliminated eventually (true if resources are limiting), e.g. when goats were introduced in Galapagos Islands, the Abingdon tortoise became extinct within a decade due to greater browsing efficiency of the goats.

(vi) Resource partitioning states that if two species compete for the same resource, they could avoid competition by choosing, for instance, different lines for feeding or different foraging patterns. In this relation, McArthur showed that five closely related species of warblers living on the same tree were able to avoid competition and coexist due to behavioral differences in their foraging activities.

Parasitism: -

It is the mode of interaction between two species in which one species (parasite)depends on the other species (host) for food and shelter and in this process the parasite damages the host. Hence, one organism is benefitted (parasite), while the other is being harmed (host).

(i) Adaptions of a parasite are: -

• Parasite is host specific in a way that both and parasite tend to coevolve. 
• Loss of unnecessary sense organs.
• The presence of adhesive organs or suckers.
• Loss of digestive system 
• High reproductive capacity.

(ii)  The life cycles of parasites are often complex, involving one or two intermediate hosts or vectors to facilitate parasitisation of its primary host, e.g.

• Human liver fluke (a trematode parasite) depends on two intermediate hosts ( a snail and a fish) to complete its life cycle.
• Malarial parasite (Plasmodium) needs a vector (mosquito) to spread disease to other hosts. 

(iii) Majority of parasites harm the host. They reduce the survival, growth and reproduction ability of the host and reduce its population density, by making it physically weak. They render the host more vulnerable to predation.

(iv) Parasites can be of the following two types 

• Ectoparasites live on the external surface of the host organism for food and shelter. Examples are the lice on humans, ticks on dogs, copepods, Cuscula, etc.
• Endoparasite's live inside the hosts body at different sites like liver, kidney, lungs, etc., for food and shelter, e.g., tapeworm, liver fluke, Plasmodium, etc. The life cycles of endoparasites are more complex because of their extreme specialization.

(v)female mosquito is not considered as parasite because it does not complete its life cycle in human body for reproduction.

(vi) Brood parasitism is a phenomenon in which one organism (parasite) lays its eggs in the nest of another organism, e.g., eggs of cuckoo (Koel) and the crow resemble in the size and colour. To reduce the chances of the crow (host) detecting the foreign eggs (cuckoo's) and ejecting them out from the nest, cuckoo lays its egg in crow's nest and let the host incubate them. 

Commensalism: -

It is the interaction between two species, where one species is benefitted and the other is neither harmed nor benefitted.

Some examples of commensalism are: -

• An orchid growing as an epiphyte on a mango tree. Orchid gets shelter and support from mango tree, while the mango tree is neither benefitted nor harmed. 
• Barnacles growing on the back of whale. Barnacles are benefitted to move to different locations for food as well as shelter, while the whales are neither benefitted nor harmed. 
• Egrets always forage close to where the cattle are grazing. Because, the cattle move, they stir up the bushes and insects are flushed out from the vegetation to be catched by cattle egrets.
• Sea anemone has stinging tentacles and the clown fish lives among them. The fish gets protection from predators, which stay away from the stinging tentacles.
• The anemone does not appear to derive any benefit by hosting the clown fish. 

Mutualism: -

It is an interaction that confers benefits to both the interacting species. 

Some examples of mutualism are: -

• Lichens represent an intimate mutualistic relationship between a fungus and photosynthesizing algae or cyanobacteria. Here, the fungus helps in the absorption of nutrients and provides protection, while algae prepare the food.
• Mycorrhizae are close mutual association between fungi and the roots of higher plants. Fungi help the plant in absorption of nutrients, while the plant provides food for the fungus.
• Plants and animals also show mutual relationship. Plants need help from animals for pollination and dispersal of seeds. In return, plants provide nectar, pollens and fruits to the pollinators, e.g. the female wasp uses the fig fruit not only as an oviposition (egg-laying) site but uses the developing seeds within the fruit for nourishing its larvae. The wasp pollinates the fig's inflorescence, while searching for suitable egg-laying sites. In return, fig provides the wasp some seeds as food for the developing wasp larvae. 
• Not all orchids offer rewards, e.g. Mediterranean orchid Ophrys employs 'sexual deceit' to get pollinated by a species of bee. One petal of its flower bears an uncanny resemblance to the female of the bee in size, colour and markings. The male bee is attracted to what it perceives as a female and pseudo copulates with the flower.
• During that process, pollen is dusted from the flower. When the same bee pseudo copulates with another flower. It transfers pollen to it and hence, pollinates the flower. This case indicates the process of coevolution. If the female bee's colour pattern changes even slightly during evolution, pollination success will be reduced unless the orchid flower coevolve to maintain the resemblance of its petal to female bee.

Amensalism: -

It is an interaction between different species, in which one species is harmed and the other is neither benefitted nor harmed, e.g. Penicillium, a Mould secretes penicillin, which kills bacteria but the Mould itself remains unaffected.

greenhouse effect| Causes, effect, Control, case study| example|

Greenhouse Effect 

It is a naturally occurring phenomenon that is responsible for heating of earth's surface and atmosphere due to the presence of certain gases in the atmosphere. 

1. In the absence of greenhouse effect, the average temperature of earth would have been chilly -l8°C rather than the present average of l5°C.
2. Clouds and gases reflect about one-fourth of the incoming solar radiation and absorb some of it. But, almost half of incoming solar radiation falls on earth's surface heating it, while a small proportion is reflected back.
3. Earth's surface re-emits heat in the form of infrared radiation, but part of this does not escape into space and atmospheric gases (e.g., carbon dioxide, methane, etc.) absorb a major fraction of it.
4. These gases radiate heat energy and a major part of which again comes to earth's surface, thus heating it up once again. This cycle is repeated again and again. 
5. The above-mentioned gases-carbon dioxide and thane are commonly known as greenhouse gases because they are responsible for the greenhouse effect. 

Global Warming 

It is the gradual and continuous increase in average temperature of surface of the earth a result of increase in concentration of greenhouse gases. 

Cause of Global Warming 

High levels of greenhouse gases (CO 2, CFCs, CH4, etc.) in the atmosphere. All these gases allow the heat waves to reach earth but prevent their escape and the earth become warm. 

Effects of Global Warming 

These are as follows: -

• Earth's temperature has increased by 0.6°C in last three decades. This ca uses change in precipitation patterns.
• The rise in temperature leads to harmful effects in environment leading to odd climatic changes, e.g., El Nino effect.
• The high temperature will result in melting of polar ice caps, which will lead to rise in sea level and many coastal areas will be submerged.
• The high level of temperature leads to increased weed growth, eruption of diseases and pests. Thus, the crop productivity will decrease. 

  

  Fig: - Relative contribution of various greenhouse gases to total global warming

  
  

Control of Global Warming: -

It can be done by: - 

1. Cutting down the use of fossil fuels. 
2. Improving efficiency of energy usage. 
3. Reducing deforestation. 
4. Planting trees, slowing down the growth of human population. 
5. Taking international initiatives to reduce the emission of greenhouse gases into the atmosphere. 

Ozone Depletion in the Stratosphere: -

• Ozone can be: - Bad ozone It is formed in troposphere and is harmful to plants and animals. 
• Good ozone It is present in stratosphere and acts as a shield, absorbing harmful UV radiation from the sun.
• The thickness of the ozone is measured in Dobson Units (DU). 
• Ozone gas is continuously formed by the action of UV-rays on molecular oxygen. 

• There should be a balance between production and degradation of ozone in the stratosphere. 
• This balance gets disrupted due to enhancement of ozone degradation by Chlorofluorocarbons (CFCs). CFCs are used as refrigerants.
• Ozone degradation When CFCs are discharged into lower part of the atmosphere, they move upward and reach the stratosphere. 
• In stratosphere, UV-rays act on them releasing chlorine (Cl) atoms.
• Cl degrades ozone releasing molecular oxygen with these atoms acting merely as catalysts.
• Cl atoms are not consumed in the reaction. 
• Hence, whatever CFCs are added to the stratosphere, they have permanent and continuous effect on ozone levels. 
• The ozone depletion is particularly marked over the Antarctic region. This led to the formation of a large area of thinned ozone layer, called as ozone hole. 

 Ozone Depletion by CFCs 

Harmful Effects of Ozone Depletion 

These are as follows: -

• UV-B damages DNA, causing mutation. 
• Ageing of skin, damage to skin cells and various types of skin cancer. 
• High dose of UV-B causes inflammation of cornea. This is called snow-blindness, cataract, etc. Such exposure may permanently damage the cornea. 

Control of Ozone Depletion 

Some measures for controlling ozone layer depletion are as follows: - 

• An international treaty, known as the Montreal Protocol, was signed at Montreal (Canada) in 1987 (effective in 1989) to control the emission of ozone depleting substances. 
• More protocols have been laid down for controlling emission of CFCs and other ozone depleting chemicals, separately for developed and developing countries. 

Degradation by Improper Resource Utilization and Maintenance 

It includes: -

1. The degradation of natural resources can occur not just by the action of pollutants, but also by improper resource utilization practices.
2. Results of improper resource utilization are: -

(a)Soil Erosion and Desertification 

• The formation of fertile topsoil takes centuries. 
• Due to human activities like overcultivation, unrestricted grazing, deforestation and poor irrigation practices, fertile topsoil is removed, resulting into arid patches of land.
• These barren patches when left for long time, form deserts. 
• Desertification is a major problem now a days due to increased urbanization.

(b)Water Logging and Soil Salinity

•  Irrigation without proper drainage of water leads to water logging in the soil.
• This leads to more salt deposition on the land surface or collection at the roots of the plants. 
• This salt content inhibits the growth of crops and damages agriculture. 
• Green revolution. has increased water logging and soil salinity. 

 Deforestation: -

It is the conversion of forested areas to non-forested areas: - 

1. Almost 40% forests have been lost in the tropics, compared to only I% in the temperate region. 
2. In India, in the beginning of the 20th century, forests covered about 30% of the land, whereas by the end of the century, it is reduced to 19.4%.
3. The National Forest Policy (1988) has recommended 33% forest cover for the plains and 67% for the hills. 

Reasons of Deforestation 

These include: - 

(i)Urbanization 

(ii) Cattle ranching 

(iii) Forest fires 

(iv) Demand of wood and other forest products

(v) Slash and burn agricultural or Jhum cultivation: -In this, Farmers cut down the trees and burn the plant remains. They ash is used as used for farming or cattle grazing. After cultivation, the area is left for several years to allow its recovery. In earlier time, enough times gap was given so that the land recovered from the effect of cultivation, this recovery phase is not available leading to deforestation.

Effects of Deforestation 

Various effect of deforestation are as follows: -

1. Increased levels of CO2concentration in the atmosphere.
2. Loss of biodiversity due to habitat destruction.
3. Disturbs hydrologic cycle.
4. Leads to soil erosion.
5. Desertification also occurs in extreme cases.

Conservation of Forests

Reforestation is the process of restoring a forest that once existed but was removed at some point of time in the past. Reforestation may occur naturally in a deforested area, or it can be speed up by planting trees.

Case Study: -People's Participation in Conservation of Forests

Case studies related to conservation of forests are as follows: -

• In 1731, a Bishnoi woman Amrita Devi (Jodhpur) showed, exemplary courage by hugging a tree and prevented it from cutting. Her three daughters and hundreds of other Bishnoi's followed her and lost their lives while saving the trees.
• The Government of India has recently instituted the Amrita Devi Bishnoi Protection Award for individuals or communities from rural areas that have shown extraordinary courage and dedication in protecting wildlife. 
• Chipko movement in Garhwal Himalayas started in 1974. Local women showed enormous courage in protecting trees from. the axe of contractors by hugging them. 
• The Government of India in 1980s has introduced the concept of Joint Forest Management (JFM), after realizing the value of participation of local communities in forest conservation. In return for their services to the forest, the communities get benefit of various forest products, thus sustainable development of forest can occur.

pollution| types| harmful effect| control methods| causes of pollution| case study| Eutrophication|

 Pollution  

It is an undesirable change in the physical, chemical and biological characteristics of air, water, land and soil.

(i) Pollutants are agents that cause undesirable change in the environment. 

(ii) The Government of India has passed the Environment Protection Act, 1986 to protect and improve the quality of our environment (air, water and soil).

Air Pollution

It is the presence of toxic chemicals or compounds (including those of biological origin) in the air, at levels that pose a health risk. Air pollutants cause injury to all living organisms. They deleteriously affect respiratory system of humans and animals.

Causes of Air Pollution 

• Smokestacks from thermal power plants, forest fires, volcanic eruptions, etc. 
• Garbage decomposition also releases unwanted gases in the air. 
• Excessive use of fossil fuels by automobiles and industries release particulate and air pollutants. 
• Use of leaded petrol.

Types of Air Pollutant 

Air pollutants can be divided into following types: -

1. Suspended Particulates Matter (SMP): -Metallic particles, dust Particles, soot, aerosol and smoke 
2. Gaseous Pollutants: - Carbon monoxide, nitrogen dioxide, hydrogen sulphide and Sulphur dioxide.

Harmful Effects of Air Pollution on Health

These effects depend on the concentration of pollutants, duration of exposure and the organism. 

1. Carbon monoxide (CO) causes giddiness, headache, cardiovascular malfunction, asphyxia, etc. 
2. Hydrogen supplied (H2S) causes nausea, eye and throat irritation. 
3. Sulphur dioxide (S02) causes respiratory tract diseases like asthma, bronchitis, cancer, emphysema, etc. 
4. Fine particulates released by industries cause breathing and respiratory problems, inflammation and damage to the lungs. 
5. In plants reduced growth and yield and premature death occurs.

Control Methods of Air Pollution 

Air pollutants must be separated/filtered out from the exhaust before releasing into the ionosphere. For this several methods are used for controlling air pollution in India. These include: -

(i)Electrostatic Precipitator (ESP) is an electrical device to re1nove particulate matter present in the exhaust of thermal power plant.  About 99% of particulate matter can be removed by ESP.

• It has electrode wires and a stage of collecting plates. 
• Electrode wires are provided with an electric current of several thousand volts, which produces a corona that releases electrons.
• These electrons get attach to the dust particles and give them negative charge within a small fraction of a second.
• Collecting plates are grounded which attract the charged dust particles. 
• The velocity of air between the plates must be low enough to allow the dust to fall. 

Figure 16.1 Electrostatic precipitotor 

(ii) Scrubber is used to remove harmful gases like Sulphur dioxide from industrial exhaust. 

Figure 16.2 Scrubber

• The exhaust is passed through a spray of water or lime. 
• Water dissolves the gases and lime reacts with sulphur dioxide to form a precipitate of calcium sulphate and sulphide.
• Drawbacks Recently, the dangers of particulate matter (very small particles that cannot be removed by these precipitators) has been found. 
• According to Central Pollution Control Board (CPCB), particulate size 2.5 micrometers or less in diameter (PM 2.5) if inhaled can cause breathing and respiratory problems, irritation, damage to lungs and premature deaths.

(iii)Catalytic convertors are fitted into automobiles for reducing emission of poisonous gases like NO2 and CO.

• They are made up expensive metals like platinum, palladium and rhodium as catalysts.
• When exhaust passes through the catalytic convertor, nitric oxide splits into nitrogen and oxygen, carbon monoxide is oxidized into carbon dioxide and unburnt hydrocarbons get burnt completely into CO2 and H20.
• However, only unleaded petrol should be used in motor vehicles fitted with catalytic convertor as leaded petrol inactivates the catalyst.

A case Study- Control of Air Pollution in Delhi: -

• Delhi leads the country in high level of air pollution due to large numbers of vehicles. In 1990s, Delhi ranked fourth among the 41 most ITI polluted cities of the world.
• As per directives of Supreme Court, all buses of Delhi were converted to run on Compressed Natural Gas (CNG) by the end of 2002. 
•  Benefits of CNG over diesel/petrol, burns most efficiently and leaves no unburnt remains. 
• Cheaper than diesel/petrol. Cannot be siphoned off by thieves and adulterated like petrol or diesel. 

Learn about Diversity in living World

• The problem with switching over to CNG is the difficulty of laying down pipelines to deliver CNG through distribution points and ensuring uninterrupted supply.
• 0ther ways to reduce vehicular pollution Phasing out of old vehicles. Use of unleaded petrol.
• Use of low-Sulphur petrol and diesel. Application of stringent pollution level norms for vehicles.
• Use of catalytic convertors in vehicles.

Auto Fuel Policy of Government of India 

• Euro II norm s stipulate that Sulphur be controlled at 350 parts per million (ppm) in diesel and 150 ppm in petrol. Aromatic hydrocarbons are to be contained at 42% of the concerned fuel.
• According to it, all automobiles have to meet the Euro III emission specification in eleven Indian cities by 1 April 2005.
• The same eleven cities have to meet the Euro IV norms by I April 2010. 
• The rest of the country will have Euro III emission norm compliant automobiles and fuels by 2010. 
• By all these efforts, a substantial fall in CO2 and S02 level has been found in Delhi between 1997 and 2005.

Note: - 

• The entire nation is next targeted to be covered under BS IV (Bharat norms under European Regulation) by 1 April 2017.
• The BS IV norms were introduced in 13 cities.
• apart from the NCR from April 2010 onwards. 
• BS IV norms stipulates the permissible limit of Sulphur to be only 50 ppm compared with 350 ppm under BS 111. Also, the limit of hydrocarbons, N02 and particulate matter emissions have been lowered further.

Noise Pollution: -

It is undesirable high level of sound. In India, the Air (Prevention and Control of Pollution) Act came into force in 1881 but was amended in l 987 to include noise as an air pollutant.

Noise Measurement 

Sound is expressed in decibels (dB). A sound of over 115 dB is very harmful for ears. Prolonged exposure to noise level above 80 dB leads to permanent hearing loss. 

Causes: -

(i) Use of loudspeakers and music systems. 

(ii) Jet planes and rockets during take-off (150 dB). 

(iii) Industrial, factory noises, etc. 

Harmful Effects: -

These include sleeplessness, stress, increased heartbeat, breathing problems, damage to ear drums and impaired hearing ability.

Control Methods: -

Noise pollution can be controlled by adopting following measures: -

(i) By using sound absorbent materials during constructions or by muffing noise in industrial units.

(ii) Delimitation of horn free zones around hospitals and schools.

(iii) Strict laws for permissible sound levels of crackers and loudspeakers sound be followed.

(iv)Loudspeakers should be played up to a fixed time only.

Water Pollution

It is any undesirable change in the physical, chemical or biological properties of water that may affect the human beings and aquatic species. The Government of India has passed the Water (Prevention and Control of Pollution) Act. 1974 to safeguard our water resources.

Sources of Water Pollution 

(i) Domestic sewage includes everything that comes from residential area to common public sewage. A mere 0.1% impurities make domestic sewage unfit for human use.

• It mainly contains biodegradable organic wastes, which are readily decomposed with the help of decomposers.
• Other components of domestic sewage are suspended solids, e.g. sand, slot and clay. 
• Colloidal materials, e.g., faecal matter. bacteria, cloth and paper fibers.
• Dissolved materials, e.g., nutrients (nittrate, ammonia, phosphate, sodium and calcium)
• During sewage treatment, it is easy to remove solid, but very difficult to remove dissolved salts such as nitrates, phosphates and toxic metal ions from wastewater.

Learn about Evolution 

(ii) Industrial wastes arc released by petroleum, paper manufacturing, metal extraction and processing units. It contains heavy metals like mercury and many organic compounds.

(iii) Heated (Thermal) wastewater flowing out of electricity genera ting units, e.g., thermal power plants. 

Harmful Effects of Water Pollution 

(i) Death of biodiversity Thermal wastewater, eliminates or reduces the number of organisms sensitive to high temperature and may enhance the growth of' plants and fish in extremely cold area s, but only after causing damage to the indigenous flora and fauna.

(ii) Biological magnification can be defined as an increase in concentration of toxicant is at successive trophic levels in aquatic food chain. Mercury and DDT arc well-known cause of biological magnification

• Toxic material cannot be metabolized or excreted. Therefore, they get accumulated in an organism and pass on to higher trophic levels.
• DDT accumulates in birds and disturbs calcium metabolism, which results in thinning of eggshell and their premature breaking. this results in decline of bird population.

(iii) Eutrophication can be defined as the natural ageing of a lake by nutrient enrichment of its water. 

Process of Eutrophication 

• Water in young lake is cold and clear to support little life. 
• Gradually with time, it gets enriched with nutrients such as nitrogen and phosphorus by streams draining in it.
• Due to this, aqua tic life (plants and animals) flourish in lake.
• Organic deposit at the bottom of the lake and with time, water becomes warmer. This warm water support even more growth of plants. Eventually, floating plants develop in the lake, finally converting it into land. Natural 
• Eutrophication generally takes 1000 of years or more. Bur, human activities have accelerated this natural process and as a result many lakes are already extinct. It is caused due to dumping of nutrient rich and thermal waste into lakes. This is known as Accelerated or cultural eutrophication.

(iv) Biochemical Oxygen Demand (BOD) is the amount of oxygen required for microbial breakdown of biodegradable organic matter. It is higher in polluted water and lesser in clean water. 

(v) Algal bloom is excessive growth of planktonic (free-floating) algae in aquatic bodies.

• In domestic sewage, nutrients like nitrogen and phosphorus Favours the growth of algal bloom. 
• It causes fish mortality and deterioration of water quality. Example, Excessive growth of water hyacinth (Eichhornia crassipes). It is the most problematic aquatic weed, also called Terror of Bengal. 
• It grows abundantly in eutrophic water bodies and imbalances water ecosystem. 

A Case Study- Integrated Wastewater Managemet: -

(i) Wastewater including sewage can be treated in an integrated manner by utilizing a mix of artificial and natural processes. 

• One such example is town of Arcata situated along. Northern coast of California. An integrated wastewater treatment process was developed with the treatment process was developed with the help of biologists from Humboldt State University in this town. The cleaning occurs in two steps: -
• (a) The heavy conventional sedimentation, filtration and chlorine treatment is carried out the treated water still contains loss of heavy metals and other toxic pollution.
• (b) In second step, algae, fungi and through which this water flows. These life forms neutralize, absorbed and assimilate the pollutants and purify the water naturally, the marshes also constitute a sanctuary, with a high level of biodiversity.
• A citizen's group called Friends of the Arcata Marsh (FOAM) are responsible for the upkeep and safeguarding of this project.

(ii) Ecosan' toilets have been developed in areas of Kerala and Sri Lanka for ecological sanitation. The advantages of ecological sanitation are:

• A practical, hygienic and efficient method of disposal. 
• Cost effective approach. 
• Human excreta can be recycled into natural fertiliser to red uce need of chemical fertiliser.

Solid Wastes 

Solid wastes refer to everything that goes out in trash. The various types are: -

• Municipal solid wastes contain wastes from homes, offices, schools, hospitals, etc, that are collected and disposed by the municipality, which generally consists of paper, leather, textile, rubber and glass, metals and plastic, elc
• Industrial wastes contain wastes like scraps, fly ash, etc. generated by industries. 
• Hospital wastes contain disinfectants and other harmful chemicals generated by hospitals. 
• Electronic wastes (e-wests) are the damaged electronic goods and irreparable computers. 
• All wastes can be categorized into Three types:

1. Biodegradable
2. Recyclable 
3. Non-biodegradable

Methods of Solid Waste Disposal 

There are various methods of solid waste disposal. Some of them are: - 

• Open burning involves burning of municipal waste in open dumps, but the unburnt piled waste serves as breeding ground for rats and flies.
• Sanitary landfills are areas where wastes are dumped in a depression or trench a ft er compaction and covered with dirt. The problem is seepage of chemicals from these landfills can pollute underground water resources. 
• Rag-pickers and kabadiwalas collect and separate out wastes int o reusable or recyclable categories.
• Natural breakdown involves dumping biodegradable materials into deep pits for natural degradation.
• Incineration is a method of hospital waste disposal. It involves burning of waste materials to ash.

e-Wastes 

• e-wastes are buried in landfills or incinerated.
• About half of thee-wastes generated in the developed world are exported to developing countries, mainly to China, India and Pakistan, where metals like copper, iron, silicon, nickel and gold are recovered during recycling process.
• Developed countries have specifically built facilities for recycling of e-wastes. 
• Recycling is the only solution available for treating e-waste, but caution should be taken to carry out this process in environment friendly ways. 

A Case Study - Remedy for Plastic Waste 

• A plastic sack manufacturer, Ahmad Khan from Bengaluru realized that plastic waste was a real problem. 
• His company developed a fine powder, called polyblend of recycled modified plastic. 
• This mixture is mixed with the bitumen and used to lay roads. 

Learn about Biodiversity

• It enhanced the bitumen's water repellant properties and helped to increase road life by a factor of three.
• Using this technique, by the year 2002, more than 40 kms of road in Bengaluru has already been laid.

Soil Pollution 

It is any undesirable change in soil profile affecting its productivity. Green revolution led to manifold increase in crop production by the use of inorganic fertilizers and pesticides. Pesticides, herbicides, fungicides, etc., are being increasingly used afterwards which resulted in soil pollution.

Causes of Soil Pollution 

(i) Chemical seepage from industries. 

(ii) Excessive use of inorganic fertilizers, pesticides, etc. 

Harmful Effects of Soil Pollution 

(i) Non-target organisms are killed in the soil, due to pesticides. 

(ii) Soil becomes unfertile. 

(iii) Pesticides can result in biomagnification, as well as eutrophication.

Control Methods 

(i) Strict ways should be adopted by the industries and other sources for waste disposal. 

(ii) Use of organic farming It is a cyclic, zero-waste method, where waste products from one process are cycled in as nutrients for other processes, allowing maximum utilization of resources and increasing the efficiency of production.

A Case Study- Organic Farming 

• Ramesh Chandra Dagar, a farmer in Sonipat (Haryana) included beekeeping, dairy management, water harvesting, composting and agriculture in a chain of processes.
• This chain supports each other and allow an extremely economical and sustainable venture.
• Chemical fertilizers are not required as cattle excreta is used as manure. 
• Crop waste is used for making compost, which is u sed as natural fertilizer or to generate natural gas, which is u sed for satisfying energy needs of farm.
• To spread information and help the practice of integrated organic farming. Dagar has created the Haryana Kisan Welfare club, with current membership of 5000 farmers.

Radioactive Wastes 

The waste produced from nuclear fission of heavy atoms such as uranium, thorium, etc., for the production of power is radioactive waste. Radiation that is given off by nuclear waste is extremely damaging to biological organisms. 

• Nuclear energy was initially considered as a non-polluting way for generating electricity initially.
• Later, two serious inherent problems were realized. The first is accidental leakages as occurred in the Three Mile Island and Chernobyl, which proved that radioactive wastes are most potent pollutants. The second is safe disposal of radioactive wastes. 

Harmful Effects 

(i) Radiations cause mutation at a very high rate. 

(ii) At high doses, nuclear radiations are lethal. 

(iii) At low doses, these cause disorders and diseases like cancer. 

Disposal method of Radioactive wastes 

It involves pretreatment and storage in shielded containers and then burying at about 500 m deep below the earth's surface. However, this method of disposal is getting opposition from public. 

Diversity in Living World, (Notes and Trick to learn), Basic of zoology, Characteristic,

The meaning of diversity is defined as the condition in which comprising several distinct elements, as gender, age, religious or ethical value of system, sexual ability, and many more.

Diversity in living world Character which define:

1. Growth 
2. Reproduction 
3. Metabolism 
4. Cellular organization 
5. Consciousness 

 All of these growth and reproduction are nondefining character and rest are defining character.

Growth: -

Increase in mass & overall increase in size of tissue organ in organism is define as growth. Region of growth is also dependent on all anabolism and catabolism activity. 

     Types of growth: -

1. Intrinsic growth (Internal growth) e.g.: - Living things. 
2. Extrinsic growth (External growth) e.g.: -Non-living. 

Two types of Intrinsic growth: - 

                                           1) Limited growth e.g.: - Animal 

                                            2)Unlimited growth e.g.: -Plant 

Reproduction: -

 It is biological process by which organism reproduce itself replica (Offspring)

Metabolism: -

 It is biochemical reaction in living it occur by constructive & destructive manner.

Consciousness: - 

All living organisms change their body according to their environment. It includes All biotic and abiotic factor. 

 DIVERSITY IN LIVING WORLD: -

• Biodiversity: -Variation in Morphological and genetical between organism on earth.
• In earth 1.7 to 1.8million species identified.

 Grouping of organisms among their diversity IN three ways: -

1. Classification
2. Identification 
3. Nomenclature  

1). Classification: -  

• Organism divided under categories and sub-categories. 
• Based on similar or dissimilar character of organism
• Classification receiving help through identification & nomenclature.

2). Identification: -

• Organism given particular place.
• Physically & biologically identification
• Identification helping classification & nomenclature.

3). Nomenclature: -

• Give name different organism (taxon)
• Given name are two types: - 

1. Common name: -

It is also known as Vernacular names. This name is reginal or local and are not universal.

for example: - The bird 'Gauraiya' in Hindi, 'house sparrow' in England, 'Pardal' in Spain, 'Musch' in Holland and so on.

2. Biological name: -

Biological name is also known as Botanical name and Scientific name. It is an universal name, biological name of a species is always a binomial name.

For example: - Triticum aestivum (Wheat)

Rule of Nomenclature 

Rule of nomenclature initially given by Linnaeus. the frame of names is mentioned in his book. "Species plantarum (1735) and systema nature" 

The rule was revised again by following nomenclature cods are: -

1). International code for botanical nomenclature (ICBN)

2). International code of zoological nomenclature (ICZN)

3). International code of bacteriological nomenclature (ICBAEN)

4). International code of viral nomenclature (ICVN)

                                                 Taxonomy 

Taxonomy is the branch of biology in which we study about identification, classification & nomenclature. Its study based on some rule and principle. Before taxonomy Linnaeus study about the classification, identification & Nomenclature in systematics way. 

                                             Type of Taxonomy

Classical Taxonomy                                           

• ü Aristotal & Theophrastus Supporter of classical Taxonomy.  
• ü Aristotal called father of classical Taxonomy.
• ü Based on external morphological character.
• ü Study pattern types of roots, stem, leaf.

Modern Taxonomy 

• ü Jullian Huxley supporter of modern Taxonomy.
• ü Father of modern Taxonomy is Linnaeus
• ü Based on Morphological & Anatomical character
• ü Study pattern cytological, Chemo logical, and molecular based.

 

                                                   Systematics

It included study of identification, Classification & Nomenclature with description.                 

                                Taxonomic Categories 

Classification not a single step process. It included series of step called taxonomic categories /taxon /rank. All categories of taxonomy constituted together Taxonomic Hierarchy 

                                  Taxonomic Hierarchy   

• It is a process of arranging different categories in descending order.
• It was first introduced by Linnaeus, so it is known as Linnaenhierachy.
  

DIFFERENT TYPE OF TAXONOMIC CATEGORIES 

  IN   PLANT   -->>   IN ANIMAL 

• Kingdom --> Kingdom 
• Division --> Phylum 
• Class --> Class 
• Order --> Order 
• Family --> Family 
• Genus --> Genus 
• Species --> Species 

Kingdom: - 

Highest categories of taxonomy.

• It includes all living organisms present on earth.
• There are five kingdom which include all organism.
• These five kingdoms are following: Monera, Protista, Fungi, Plant, Animalia.

Phylum: - 

It is higher categories of taxonomy; it includes CLASS Which help some similar character.

e.g.: - Phylum: - 'Chordata' It include class Pisces, Amphibia, Reptiles, Anus and Mammalia.

Class: -  

This category includes related orders. For example, order primate comprising monkey, gorilla and gibbon is placed in class Mammalia along with order Carnivora that includes animalia tiger, cat and dog.

Order: -

Generally, order and other higher taxonomic categories are identified based on the aggregates of characters. Order being a higher category is the assembled of families which exhibit a few similar characteristics. 

Family: - 

Families are characterized on the basis of both vegetative and reproductive features of plant species. Among plants for example, three different genera Solanum, Petunia and Datura are placed in the family Solanaceae.

Genus: -

Genus comprises a group of related species which has more characteristics is similar in comparison to species of other genera. Genera is closely related to species.

Species: -

It is taxonomic group of single organisms with their fundamental similarity which is represent the specific epithets.

Evolution: Origin of life| Earth| Artificial selection |

The study of history of lifeforms on earth is, called evolutionary biology. Evolution is a process that results in heritable changes which spread over many generations, leading to diversity of organisms on earth. In simple words, evolution is the sequence of gradual changes from simple life forms to complex life firms over millions of years

Origin of Life 

It is considered a unique event in the history of our universe.

Origin of Universe: -

✅It is about 20 billion years old. It contains huge galaxies.

✅ Galaxies conations stars and clausa of gas and dust.

✅ The origin of universe is explained by big bang theory given by Abbe Lemaitre in 1931.

✅The Big Bang Theory states that the universe arose from, a huge explosion. As the universe expanded, temperature came down and hydrogen and helium were formed later. The galaxies were then formed due to condensation of gases under gravitation.

Origin of earth: -

It was supposed to be formed about 4.5 billion years back in the solar system of the milky way galaxy.

✅Water vapor, methane, carbon dioxide and ammonia released from molten masses covered the surface. 

✅UV rays from the sun broke up water molecule into hydrogen and oxygen and lighter hydrogen escaped. 

✅ Oxygen combined with ammonia and methane to form water, carbon dioxide and other compounds. 

✅ Subsequently Ozone layer formed. As earth cooled, the water vapour fell as rain to fill depression and formed oceans.

✅ Life appeared 500 million (about 4 billion years back) years after the formation of earth.

Theories of Origin of Life: -

Various theories of origin of life were given by different thinkers and scientists. These are as follows: -

✅Theory of special creation states that God created life by his divine act of creation. 1t was proposed by Father Suarez.

✅Theory of panspermia/cosmogonic states that the spores or panspermia came from outer space and developed into living fronts. It was given by Arrhenius.

✅ Theory of spontaneous generation states that life originated from decaying and rotting matter like straw, mud, etc. This theory is also known as theory of abiogenesis or auto biogenesis. 

✅Louis Pasteur rejected the theory of spontaneous generation and demonstrated that life came from pre-existing life.

✅ In his experiment, he kept killed yeast cells in presterilized flask and another flask open into air. The life did not evolve in the former but new living organisn1s evolved in the second flask.

✅Theory of chemical evolution or Oparin-Haldane theory states that life originated from pre-existing non-living organic molecules and that formation of life was preceded by chemical evolution. The condition s on the earth that favored chemical evolution were very high ten1perature, volcaruc storms and reducing atmosphere that contained CH4, NH3, water vapor, etc. 

Experimental Evidence of Chemical Evolution: -

Miller's experiment provided experimental evidence for chemical evolution.

✅The experiment was carried out by SL Miller and HC Urey in 1953. 

✅They took a closed flask containing CH4, H2, NH 3 in the ratio of 2: 2: land water vapor at 800°C and created electric discharge. These conditions were similar to those in primitive atmosphere. 

✅ After a week, formation of amino acids was observed. Complex molecules like sugars, nitrogen bases, pigments and fats were seen in the flask by other scientists.

✅ Miller and Urey supported the idea of abiogenesis followed by chemical evolution. Analysis of the meteorite also revealed the presence of similar compounds.

✅ Chemical evolution of life was more or less accepted.

Origin of First Cell: -

✅ First non-cellular lifeforms originated three million years ago. These molecules were like RNA, protein and polysaccharides inside a self-replicating metabolic capsule which later reproduced its molecules.

✅ Cellular lifeform first evolved about 2000 million years ago. These were single-celled and formed in aquatic environment.

✅This form of abiogenesis, i.e., the first form of life arose slowly through evolutionary forces from non-living molecules, was accepted by many scientists.

Evidence of Evolution: -

 Evidence that suggests that evolution has occurred on earth are derived from: -

(i) Palaeontology

(ii) comparative anatomy and morphology

(iii) Biochemical/Physiology

(iv) Biogeography 

(v) Embryology

Paleontological Evidence: -

(i) Paleontology is the study of fossils. The fossils are the remains of past organisms preserved in sedimentary rocks. 

(ii) Rocks form sediments and a cross-section of earth's crust indicates the arrangement of sediments one over the other during the long history of earth.

(iii) Different aged rock sediments contain fossils of different lifeforms, who died during the formation of particular sediment. 

(iv) Some organisms appear similar to modern organisms. They represent extinct organisms like dinosaurs.

(v) A study of fossils in different sedimentary layers indicates the geological period in which they existed. Fossils which are obtained from old rocks arc of simple ty pe, while which were obtained from new rocks are of complex type.

(vi) The study showed that lifeforms varied over time and certain lifeforms are restricted to certain geological time scale. Hence, new forms of life have evolved at different times in the history of earth.

Comparative Anatomy and Morphological Evidences; -

These studies high light the similarities and differences among the organisms of today and those that existed years ago. The evidence come from comparative study of external and internal structure.

Homology: -

✔ In an organism, the homology indicates common ancestry. 

✔ The organs with same structural design and origin hut different functions arc called homologous organs. For example, forelimbs of some animals like whales, bats and cheetah have similar anatomical structure, such as humerus, radius, ulna, carpals, metacarpals and phalanges. But these forelimbs perform different functions in these animals. Other examples of homology arc vertebrate heart and brain.

✔ In plants, thorns and tendrils of Bougainvillea and Cucurbita represent homology. 

✔ Homology is based on divergent evolution. The same structure developed along different directions due to adaptations to different needs. The condition is called divergent evolution.

Fig: - Homologous organs in animal (forelimb)

Analogy: - 

✔It refers to a situation exactly opposite to homology. 

✔ Organs which are anatomically different but functionally similar are called analogous organs. For example, wings of butterfly and birds. In both, wings perform same function, but they have different origin and structure.

✔Analogous organs arc a res ult of convergent evolution. It is the evolution in which d 'ferent structures evolve for same function and hence, have similarity. It can be said that above organisms had different structures, but they came in the same environment and evolved to perform same function.

✔Other examples of' analogy are eyes of Octopus and mammals, flippers of penguins and dolphins. In plants, sweet potato (root modification) and potato (stem modification) are analogous, structures.

Vestigial Organs: -

Like homologous organs, these organ s also provide evidence for organic evolution. These are degenerate, non-functional and rudimentary organs to the possessor, while correspond to fully developed and functional organs of related organisms.

✔There are about 90 vestigial organs in the human body. Some of them are tail bone (coccyx), wisdom teeth, nictitating membrane, vermiform appendix, etc. 

✔ Some examples from other animals are hip girdles and bones of the hindlimbs in some whales and certain snakes and wings of f1ightless birds.

Biochemical Evidences: - 

✔ The metabolic processes in organisms are similar with some new materials and end product. For example, energy released by oxidation is stored in ATP, which then provide power for energy requiring process.

✔Molecular homology is the similarity among animals at the molecular level. For example, human DNA differs in only 1.8% of its base pairs from chimpanzee's DNA and there is no difference between the two in the amino acid sequence for the protein cytochrome-c.

✔In the same way, enzymes, proteins and genes perform same functions in different organisms. So, it indicates common ancestry among organisms.

Biogeographical Evidence: -

The species restricted to a region, develop unique features. Also, species present in far separated regions show similarity of ancestor. This can be explained with the help of following processes.

Adaptive Radiation: -

It is an evolutionary process in which an ancestral stock gives rise to new species that are adapted to new habitats and new ways of life. In other words, adaptive radiation is evolution of organisms, starting from a point which then radiate or spreads to other habitats. Examples are: -

(i) Darwin's finches These were small black birds, which Darwin observed in Galapagos Island. 

(a) He observed many varieties of finches in the same Island. 

(b) All varieties of finches had evolved from original seed-eating finches.

(c) There was alternation in beaks enabling to become insectivorous and some vegetarian. All these varieties evolved from original species due to different type of food available at different Island.

(ii) Marsupials of Australia A number of marsupials (mammals with pouch), Different from each other evolved form an ancestral stock, all within the Australian Island continent.

Convergent Evolution: -

It is the occurrence of more than one adaptive radiation in an isolated geographical. area with different habitats. Examples are: -

✔Wings of insect, bird and bat.

✔Spiny anteater and scaly anteater belong to different orders of class Mammalia. They have acquired similar adaptations for food, e.g., leg ants, termites and insects.

Parallel Evolution: -

It refers to independent development of similar characters in two animal groups of common ancestry living in similar habitats of different continents. Examples are: - 

(iii) Placental mammals in Australia show parallel evolution as they have evolved from marsupial mammals. All these closely resemble and look similar to a corresponding marsupial.

Embryological Evidence: - 

The study of comparative embryology shows common pattern of development.

1. The principles of embryonic development were given by Von Baer.
2. Ernst Haeckel propounded the theory of recapitulation or Biogenetic law, which states that an individual organism in its development (ontogeny) tends to repeat the stages passed through by its ancestors (phylogeny), i.e., ontogeny recapitulates phylogeny.
3. This means that the life history of animals reflects its evolutionary history. For example, during the life history, Frog's tadpole larva resembles fishes, the ancestors of amphibia. The presence of gill clefts in all vertebrate embryos including human provides strong embryological evidence.

Anthropogenic Evidence: -

Excess use of herbicides, pesticides, etc. has resulted in selection of resistant varieties in a lesser time scale. This is also true for microbes against which antibiotics or drugs have been used. All this evidence reflects that 'Evolution is a stochastic process based on chance events in nature and chance mutation in the organisms.

Artificial Selection: -

Human has created many varieties of plants and many breeds of animals for his use by domestication of wild varieties, selection and carrying out intensive breeding programs. So, if human can create new species why not nature.