Organisms And Populations

Autecology is a branch of ecology which deals with the relationship between an individual and its environment.

Ecotone is a zone of transition between two communities. In ecotone the two communities meet and integrate. Example: Grasslands between forests and deserts. Here forests and deserts are two separate communities and the grassland is the ecotone, where the communities meet and integrate. Ecotone has intermediate conditions.

Biosphere is composed of all living organisms present on earth which interact with the physical environment

An ecological niche is the physical position in the food chain and the functional role of a species in the environment.An ecological niche tells us about :

1. How the species reproduce, get its food and shelter?

2. How it tackles with its enemy.

3. It also tells us about the interaction of the species with the biotic and abiotic environment.

According to Allen’s Rule, the mammals from colder climates have shorter ears and shorter limbs. These adaptations help to retain heat and minimise heat loss. If the surface area of ears and limbs would be more the amount of heat loss would increase. So, lesser surface area is required hence shorter ear and limbs.

Mean Annual Temperature: It is the average of the maximum and the minimum temperature of a year.

Mean Annual Precipitation: It is the average of the maximum and minimum precipitation in an year.

Tall trees control the light conditions at the ground.

Because of the very dense canopy, little sunlight reaches the ground. In a dense forest, the canopy trees can block out over 95% of the sunlight. So tall trees control how much light is available to rest of the forest plants.

In a forest the herbaceous plants get less intensity of light as the tall trees control the light on the ground but once if a well growing herbaceous plant in the forest is transplanted outside the forest in a park, it is exposed to high intensity of light and change in its micro environment occurs so the plant may not survive.

Initial population of Paramecium (Pi): =50

Growth of Paramecium after 1 hour (Pf)=150

Growth Rate=Pi-Pf

=150-50=100

Hence, the growth rate would be 100.

As per question 10,

Initial population of paramecium, P_i = 50

Final population of paramecium after one hour, P_f = 150

So the per cent growth or birth rate per individual per hour will be

Hence the correct answer is option (b).

In the population having more young individuals than older individuals there will be rapid increase in the young ones after some years as the birth rate will increase and death rate would decrease.

Hence the correct answer is option (c).

The parameters that are used for tiger census in our country’s national parks and sanctuaries are often based on pug marks and faecal pellets.

Hence the correct answer is option (b).

Mortality and emigration would decrease the density of a population in a given habitat. Mortality is the number of deaths in the population and emigration is number of individuals of the population who left the habitat and went into some other population. In both these situation the number of individuals in the population would decrease and hence the density decreases.

Hence the correct answer is option (c).

The number of protozoans in its population after six generations = 64.

Binary fission is doubling in numbers every day.

So population due to binary fission will be 2ⁿ after n generations.

Similarly population of protozoans after six generations will be (2⁶=64).

Hence the correct answer is option (c).

The required exponential equation is,

Where N = Population size

t = time period

r = ‘intrinsic rate of natural increase’ = b-d

d = death rates

b = birth rates

From the given criteria,

N₂₀₀₅ = 14 million

b = 0.028

d = 0.008

∴ r = b-d = 0.028 – 0008 = 0.020

dt = 2015 – 2005 = 10 years

Using exponential equation,

⇒ dN = 0.28×10 = 2.8

We know

dN = N₂₀₁₅- N₂₀₀₅

⇒ N₂₀₁₅= dN + N₂₀₀₅ = 2.8 + 14 = 16.8 ≈ 17 millions

Using exponential equation, the number of people present in 2015 is predicted as 17 millions.

Hence the correct answer is option (b).

Amensalism is a type of population interaction where one species is harmed and other is unaffected.

Hence the correct answer is option (b).

Lichens represents mutualistic association between fungus and algae (also known as cynobacteria).

Hence the correct answer is option (c).

Sandalwood is a partial root parasite. Mistletoe (Viscum) is considered as hemiparasite which derives a part of nourishment from host plant. Orobanche is a holoparasite which infects species from favciae i.e., beans, ioranlhus. Ganodermna are parasite for example basidiocarpic mushrooms.

Hence the correct answer is option (a).

Banana is a monocarpic plant which reproduces sexually only once in its life time

Species that can tolerate narrow range of temperature are called Stenothermal species. They are further divided into two categories:

1. Thermophilic: These organisms can only tolerate high range of temperatures. Example includes coral reefs.

2. Cryophilic: These organisms can only tolerate low range of temperatures. Example includes seals, salmons.

Eurythmic species are those organisms that can adapt to wide range of temperature changes. These can survive in extremes temperatures. Example includes cats, dogs and tiger.

Species that can tolerate wide range of salinity are called Euryhaline.

Stenohaline are those species which cannot tolerate fluctuations in the degree of salt in the water, that is salinity of the surrounding water. Example: Goldfish dies in water with high salinity like ocean whereas haddock fish dies in water with low salinity.

A biological interaction is the effect that pair of organisms that live together in a community have on each other.

If the interaction is between same species, it is called intraspecific interaction.

A long-term interaction is called a symbiosis.

Symbioses can be of different types: mutualism, commensalism, predation, competition, etc.

Commensalism is the type of interaction between two species in which one species gets benefited by the other and the other species does not get affected. Example: Pseudo scorpions are tiny scorpions. They ride on other larger insects. This interaction protects them from predators and they easily get transported. The larger insects are not harmed but they don’t gain anything from them either.

Such an interaction is known as Ammensalism. In this interaction one species gets destroyed and the other species remains unaffected. Example Black walnut destroys the roots of the plant on which it grows and itself remains unaffected.

Mycorrhiza is a type of fungi. It grows in association with the plant roots. This relationship benefits the plants as:

1. Mycorrhiza increases the ability of the roots to absorb nutrients from the soil. This happens because the surface area of the roots increases. In turn absorption capacity also increases.

2. Mycorrhiza releases enzyme that helps to dissolve nutrients.

3. It also improves crop quality.

4. In turn mycorrhiza gets shelter.

Emergent land plants that can tolerate the salinities of the sea are called Mangrove plants.

High altitude areas have brighter sunlight and lower temperatures because of thinner atmosphere and absence of dust particle.
Brighter sunlight: There is little diffraction of incoming sunlight so that the latter is brighter.
Lower temperature: Atmosphere is unable to block the outgoing infra red rays. There is little retention of heat. The light appears to be brighter. Due to low atmospheric pressure the temperature also remains low.

Homeostasis is the tendency of the organism to maintain a constant internal environment despite varying external environmental conditions like temperature.

Aestivation is a behavioural adaptation to avoid extreme heat and desiccation in summer season. It is a state of dormancy in which the organism slows down its metabolic activities and is inactive. It is also known as summer sleep.

Diapause is a type of adaptation to survive during unfavourable conditions. Diapause is a stage of suspended development in some organisms like zooplanktons in lakes and ponds.

When the resources are unlimited the growth rate pattern would be exponential in nature.

The organisms that feed on plant sap and other plant parts called Phytophagous example insects and other invertebrates.

High altitude sickness is also known as mountain sickness. This is experienced by those people going to high altitudes. High altitude sickness usually arises due to decrease in the amount of oxygen which occurs at high altitude. It is a apthological effect which is caused by acute exposure to low partial pressure of oxygen at high altitudes.

The symptoms of high altitutde sickness are:

- Breathlessness

- Fast breathing

- Nausea

- Vomiting

- Headache

- Muscular weakness

- Mental Fatigue

Interaction between blue whale and barnacle growing on its back is an example of commensalism.

Commensalism is a positive interaction between species in which one species is benefitted and other species is unaffected i.e., neither benefitted nor harmed.

Interaction between cattle egret and grazing cattle is an also an example of commensalism.

Ecoparasite are parasite that feed on the external surface of the host organism and generally attach themselves during feeding. Example – Lice on humans, ticks on dogs, etc.

Endoparasites are parasite that lives inside the host body at different places like kidney, lungs, red blood cells, etc. Example – human liver fluke, tapeworm, malarial parasites, etc

Brood parasitism is a type of parasitism in which an organism lays eggs on the nest of another organism.

Example – cuckoo lays eggs in the nest of its host and the host incubate the eggs. The eggs are similar to the host eggs in terms of size and colour, this reduces the chances of the host bird detecting the foreign eggs and ejecting them out of the nest.

Coral reefs are underwater structures composed of skeletons of colonial marine invertebrates. They are formed in the areas having following conditions:

1. Tropical areas are required. These are the areas near equator.

2. High salinity is required. Water having high salt content is needed.

3. Influx of fresh water should not be there.

4. No siltation should occur. This means accumulation of fine mineral particles in the water should not take place.

All these conditions are favourable in Tamil Nadu and on the east coast of India but are not found in the regions from west Bengal to Andhra Pradesh

If a freshwater fish is placed in an aquarium containing sea water the fish may not survive. Marine or sea fish is exposed to high salt concentration. Whereas freshwater fish is exposed to low salt concentration. This change of salinity leads to disturbance in osmotic pressure. The amount of water exiting the freshwater fish’s body increases and it dies due to dehydration.

Contractile vacuole helps in removal of excess water from the body. Marine fish are exposed to high salinity. So, there is no need to remove excess water as osmotic balance between the surrounding water and fish’s body is maintained. Fresh water fish are exposed to low salt concentration. So, they require contractile vacuoles to remove excess water.

Heliophytes are also known as sun loving plants. These plants require high intensity sunlight for optimum growth. Example Thyme, sunflower etc.

Sciophytes are also known as shade loving plants. These plants require low intensity sunlight for optimum growth. Example Lycopodium.

Submerged plants are underwater plants. These plants receive weaker illumination because the sunlight reaches the plant by passing through deep water. Floating plants are exposed to high intensity sunlight because they float on the surface of the water. Sunlight directly reaches the plant.

Benthic animals are those which live near the sea bed ,river, lake or bottom of the stream .

(a) The three tiers represent:

Tier 1: Pre-reproductive population

Tier 2: Reproductive population

Tier 3: Post Reproductive population

(b) The pyramid represents growing or expanding population as the pre-reproductive and reproductive population is growing.

The association in which one is termite and other is Trichonympha is a type of mutualism relation.

The termite provides shelter and space for the protozoan to live. The Protozoa present in gut digests the wood, which termite eats. In the absence of Trichonympha the termite is unable to digest wood and hence dies. Thus, the association of two given animal species represent mutualism that is both the interacting species are benefitted.

The association in which one is Lianas and other is trees is commensalism.

The Lianas plant has long, flexible stem, it gets the support of the tree without affecting harming or providing any benefit to the tree.

With the help of the tree, the Lianas are able to expose its leaves to the sunlight.

Thus, the association of Lianas and tree represent commensalism that is one species is benefitted and the other is neither benefitted nor harmed

The scientific names of two microorganisms inhabiting the human intestine are Escherichia coli and Lactobacillus.

Tree line is an altitude beyond which no tree is seen.

Due to environmental conditions such as cold temperature, high altitude or lack of moisture the trees are not found beyond this line and if found show stunted growth or form low dense matted bushes. So beyond tree line only shrubs and hers are found.

Zero Population growth rate is a condition wherein the population neither grows nor declines.

In this condition the pre-reproductive age group individuals are less in number and both reproductive and post-reproductive stages are almost in equal stage, i.e., at same level.

An inverted bell shaped age pyramid is obtained for zero population growth rate.

The characters that are employed in human population census are:

- Natality and mortality – Natality (birth rate) is the production of new individual of any organisms per unit of population per unit time, mortality (death rate) is the rate of death of individuals per unit time.

- Sex ratio – it is the proportion of males to females in a given population, usually expressed as the number of males per 100 females at specific stage in life.

- Population density – It is the number of individuals of a species per unit area or space at a given time.

- Age distribution – It is the number or percentage of individuals in a population in different age group.

a) Migratory animal – Siberian crane, salmon, dolphin, etc

b) Camouflaged animal – Grasshopper, chameleon, Frog, etc

c) Predator animal – Tiger, sparrow, lion, etc

d) Biological control agent - Myxoma virus to kill European rabbit, Gambusia fish to check growth of mosquito larvae, moth against prickly pear cactus, etc

e) Phytophagous animal – Locusta insect, beetle, butterfly, etc

f) Chemical defense agent – Cardiac glycosides produced by Calotropis

i. Figure A shows mutualism, this interaction confers benefits on both the interacting species. Figure A shows a pollinator (bee) on a flower.

ii. Figure D shows an association of predation, in this type of interaction only one species benefits. In this figure leopard is eating deer.

iii. Figure C shows egrets and grazing cattle. The association in this figure is commensalism, here one species is benefitted and the other is neither benefitted nor harmed.

iv. In figure B the insect is phytophagous that feed on sap of the flower. The insect is playing the role of a scavenger. Scavenger is an animal that feeds on dead organisms.

The given three figures are showing species in an environment.

1. Figure 1 shows a single population (A). All individuals of the same species are interacting among themselves and their environment only.

2. Figure 2 shows three species which are A, B and These three species are interacting among themselves and their environment.

3. Figure 3 shows a biome. It has three communities. Each community has different species. These three communities are interacting with each other and the environment forming a biome.

A population has varied characteristics than an individual. Some of which are:

A) A population has birth rate (natality) and death rate (mortality) whereas an individual has birth and death.

1. An individual is either male or female. A population has sex ratio which the number of females per 1000 males.

2. A population has different age groups whereas an individual is of specific age.

B) Population Density: It is the number of individuals per unit area. This density changes with time and space. Example: There are 500 insects per 100 km square. It is calculated by quadrant method, direct or indirect observations.

C) Population Growth: It is the growth rate seen in a population over time. It is represented by population growth curve where number of individuals are plotted on the y-axis and the time is plotted on the x-axis. A curve is obtained showing the growth or decline in a population. It is of two kinds S shaped sigmoid curve and J shaped curve. Example:

D) Natality: It is the rate of reproduction or birth rate per unit time. Increased natality shows increasing population. It can be calculated by the following method:

NUMBER OF BIRTHS PER UNIT TIME/AVERAGE POPULATION X 1000

E) Mortality: It is the rate of deaths per unit time. Increased mortality shows a decline in population. It can be calculated by the following method:

Number of Deaths/Time

The given figures represent a population pyramid. The base is the pre-reproductive population.Mid part is the reproductive population and the top is the post reproductive population.

Figure ‘A’ is a pyramid shaped figure. This structure has a larger base than the mid and the top. This large base indicates greater pre-reproductive population than reproductive and post reproductive population.

Status: This shape indicates population would grow rapidly.

Figure ‘B’ is an inverted bell-shapedpyramid. Inthis both pre-reproductive and reproductive population is the same.

Status: This shape indicates population is stable.

Figure ‘c’is an urn shaped pyramid. The pre-reproductive and reproductive population is lesser than the post reproductive population. They have more older people than young generation.

Status: This shows that the population is declining.

The given graph shows a population growing in a habitat having limited resources.

1. The graph shows an initial lag phase. After that an increase in population takes place known as acceleration following which deceleration takes place and at last asymptote occurs.

2.When the population reaches carrying capacity. A plot is formed showing sigmoid curve.

3. This type of growth is known as Verhulst-Pearl logistic growth.

4. This is represented by an equation: dN/dT=rN(K-N/K)

dN/dT=rN(1-N/K)

Here, (1-N/K) is environmental resistance

As the population of Paramoecium caudatum was grown in a culture medium. After 5 days the culture medium became overcrowded with Paramoeium and had depleted nutrients because after the overcrowding of paramoecium the nutrients became limited and got depleted.

Sigmoid type of growth curve would be obtained. Which shows a population growing in a habitat having limited resources.

The graph obtained is shown below:

1.The graph shows an initial lag phase. After that an increase in population takes place due to the availability of nutrients also known as acceleration. Following which deceleration takes place as the available nutrients got depleted because of excessive usage and growth of paramoecium stops. At last asymptote occurs.

2.When the population reaches carrying capacity. A plot is formed showing sigmoid curve.

3.This type of growth is known as Verhulst-Pearl logistic growth.

4.This is represented by an equation: dN/dT=rN(K-N/K)

dN/dT=rN(1-N/K)

Here, (1-N/K) is environmental resistance

Various types of positive interaction between species are as follows:

i. Scavenging - Scavenger is an animal that feeds on dead organisms.

Examples –

> phytophagous that feed on sap of the flower.

ii. Commensalism – In this inter-specific interaction one species benefits and the other is neither harmed nor benefited.

Examples –

> An orchid growing as an epiphyte on a mango branch

> barnacles growing on the back of a whale

> cattle egret and grazing cattle

> sea anemone that has stinging tentacles and the clown fish that lives among them to get protection from the predators.

iii. Proto-cooperation - This inter-specific interaction benefits both the interacting species. In this both the species can live without each other unlike mutualism association

Examples –

> Crocodile bird rids crocodile of leeches sticking inside the mouth of the crocodile.

iv. Mutualism - This inter-specific interaction benefits both the interacting species. Here the growth and survival of both the species id benefitted and neither of them can survive without the other species under natural condition.

Examples –

> Lichens shows an intimate mutualistic relationship between a fungus and photosynthesising algae or cyanobacteria.

> Mycorrhizae are associations between fungi and the roots of higher plants. The fungi help the plant in the absorption of essential nutrients from the soil while the plant in turn provides the fungi with energy-yielding carbohydrates.

> Plants offer nectar, juicy and nutritious fruits to animals and they help to pollinate their flowers and disperse their seeds.

In the given condition competition interaction is taking place.

Competition is a rivalry relationship between two or more organisms.

A competition between individual of same species (intra specific) is more serious as compared to intraspecific competition between individuals of different species as all the members in a interspecific competition have same basic requirements like food, water, light, space, mating and shelter. But this is true only when resources are limited.

Each species has a specific role within their niche.

According to Gause's principle, one of the species is to be eliminated, i.e., no two species can live in a same niche and hence one of them need to be eliminated. But in the given scenario two herbivorous species are living in the same niche and feeding on phytoplanktons may be due to sufficient availability of phytoplanktons.

And as soon as the resources (i.e., phytoplanktons) starts to finish, the fishes would compete with each other as a result the competitively inferior one will be eliminated eventually.

And if the resources is plenty of the two species neither may be eliminated and niche overlapping may affect the growth and development of the individual.

Parasites have evolved special adaptations while living on and in the host species they are as follows:

(i) The loss of unnecessary sense organs for example: lice, mites and fleas don't have wings.

(ii) Presence of adhesive organs or suckers to cling on to the host for example - in tapeworms and leeches.

(iii) Loss of digestive system i.e., tapeworm.

(iv) High reproductive capacity i.e., roundworm produces large progeny.

Yes regional and local variations exist within each biome.

A biome can be defined as the large communities of the world. Climate is the main factor that determine the type of soil which in turn determines the type of vegetation. The type of vegetation and climate together determine the kind of microorganisms and animals.

The main biome of the world does not show boundary of any country. Regional and local variations lead to formation of a wide variety of habitats.

For examples:

> On earth, life exists even in extreme and harsh habitats – scorching Rajasthan desert, perpetually rain-soaked Meghalaya forest, deep ocean trenches, torrential streams, permafrost Polar Regions, hign mountain tops, boiling thermal springs and stinking compost pits, etc.

> Even our intestine is a unique habitat for hundreds of species of microbes.

> Temperate deciduous forest receive an annual precipitation between 75-150 cm and tropical rain forest show a rainfall above 140 cm/yr which may reach upto 400 cm/yr.

The elements responsible for causing soil salinity are Na⁺, K⁺, Ca²⁺, Mg²⁺ and Cl^-.

Soil salinity is the salt content in soil, which is caused by improper irrigation. Causes of Soil Salinity are:

> improper irrigation

> Human activities like fertilizing crop

Salinity of soil degrades soil and vegetation. Normally the pH value of soil is in between 2.2 - 9.7 above which the soil is degrading by salt content.

Yes light factor affect the distribution of organisms.

Since plants require sunlight for photosynthesis and to produce food. And photosynthesis is possible only in presence of sunlight. Therefore, light is an important factor that affects the distribution of plants.

For examples:

(i) Many species of small plants (herbs and shrubs) growing in forests are adapted to photosynthesize optimally under very low light conditions so they will be seen distributed in shady areas under tall, canopied trees. The small plants in the forests are usually overshadowed by tall, canopied trees.

(ii) Many plants are also dependent on sunlight to meet their photoperiodic requirement for flowering.

(iii) Many plants in the shade will grow vertically to gain access to light. These plants will appear to have smaller leaves than other plants of the same species of the same age found in conditions with better sunlight.

(iv) Large sized trees will be present in areas that get abundant sunlight,

(v) Plants dependent on sunlight to meet their photoperiodic requirements for flowering, will try to be distributed in area, where this requirement is being met for their reproductive success.

i. Eurythermal plant species – Mango, red algae, acacia

ii. A hot water spring organism – Thermus aquaticus, Archaebacteria

iii. An organism seen in deep ocean trenches – Jelly fishes, Sea cucumbers

iv. An organism seen in compost pit – Earthworm, fungi, bacteria

v. A parasitic angiosperm - Cuscuta reflexa

vi. A stenothermal plant species – Conifers, Cocosnucifera

vii. Soil organism – Bacteria, Earthworm

viii. A benthic animal – Crabs, sponges, Octopus

ix. Antifreeze compound seen in antarctic fish – Salt content, antifreeze glycoproteins or AFGPs

x. An organism which can conform – Frog, All plant and fish like largemouth bass (temperature conformer)