Biology Chapter 13 Organisms And Populations

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Age distribution (Age composition). The relative abundance of the organisms of various age groups in the population is called age distribution of population.It gives a status of the growth of the population.

 Age structure of hypothetical populations which are expected to increase, remain stable or decline with the passage of time.
(a) Expanding Population - In this the number individual in pre-reproductive stage and reproductive stage are more than the individuals in the post-reproductive stage, so the growth of population is high.
(b) Stable population. It has equal number of individuals in all stages , so population shows no growth.
(c) Declining population. It has higher number of individuals in the post reproductive stages so the  population of young members is lower than that of old members and hence growth is retarded.

Parasite. The organism, which obtains its food or nourishment from the other without directly killing it, is known as parasite.
Host. The second organism which provides food and harbours the parasite is named as host.

Parasites are of two kinds-
Endoparasite is the parasite that lives inside the body of the host.

Ectoparasite is the parasite which lives on the outside of the body of the host e.g. Leech, Louse, Bed bug.

Example. Cuckoo birds lays eggs in the nest of crows.

1. Loss of unnecessary sense organs.

2. Presence of hooks/adhesive organs and suckers.

3. Loss of digestive system and high reproductive capacity.

4. They have become host specific and co-evolve with the host to counteract the mechanisms by which the host resists it.

Examples. 1. Mutualism between Rhizobium and leguminous plants. The rhizobium bacteria helps the plant to fix nitrogen whereas the plant provides food and shelter to the bacteria.

2.Mutualism between plants and fungus. Lichens involve the symbiotic association of a green alga and a fungus. The fungus provides protection to algae whereas the algae provides food to the fungus

Example. Orchids grow as epiphytes on the mango tree. The orchids use the tree as a support for growth , whereas the mango tree is neither harmed nor benefited.

Emigration. It is  outward movement of some individuals of the species from a local population  during the time period under consideration. It leads to decrease of size of local population.

It states that  two closely related species competing for the same resource cannot co-exist indefiinitely, and it eventually leads to the elimination of the inferior species.

Example. Desert plants have sunken stomata to prevent loss of water.

(ii) Evolution - A whole species of the population evolves and not an individual.

(iii) Population density is the number of inviduals per unit area at a given time. 

(iv) Sex Ratio- It is the number of males to females in a given population.

(v) Age distribution is percentage of individuals of a given age or age group in the given population.

The exponential growth can be calculated by the following integral form of the exponential growth equation:

N_t = N_o e^rt

Where,

N_t= Population density after time t

N_O= Population density at time zero

r = Intrinsic rate of natural increase

e = Base of natural logarithms (2.71828)

Now, as per the question,

Present population density = x

Then, Population density after two years = 2x

t = 3 years

Substituting these values into the formula, we get:

⇒ 2x = x e^3r

⇒ 2 = e^3r

Applying log on both sides:

⇒ log 2 = 3r log e

Hence, the intrinsic rate of increase for the above-illustrated population is 0.2311.

1. Formation of leaf spines e.g. leaf spines in Opuntia

2. Modification of leaves into thorns, e.g. Bougainvillea and Duranta.

3. Development of spiny margins on leaves.

4. Development of sharp silicated edges in leaves.

5. Many plants produce and store toxic chemicals which cause discomforts to herbivores e.g. cardiac glucoside by Calotropis, Nicotine by tobacoo.

(b) Differences between ectotherms and endotherms

Three important characteristics of a population are:
(i) Population size and population density-  is the number of individuals or organisms per unit area or  unit volume. It is denoted by N.
(ii) Birth or natality rate- It is generally expressed as number or births per 1,000 individuals of a population per year. It increases the population size (total number of individuals of a population) and population density.
(iii) Death or mortality rate - Death or Mortality rate. It is  the number of deaths per 1,000 individuals of a population per year.

Population density is the measure of number of individuals in a population. It  is expressed as number of individuals in a definite area at a specific time. 

Examples,
(i) A tiger(predator) killing and eating a deer(prey).

(ii) A snake (predator) eating a frog (prey).

1. They act as ‘conduits’ for energy transfer to higher trophic levels.

2. They keep the prey population under control, which otherwise can reach very high population density and cause imbalance in the ecosystem.

3. They help in maintaining species diversity in a community by reducing the intensity of competition among the competing prey species.

The two processes which result in increase in population are-:
i. Natality
ii. Immigration.

1. Light. 2. Temperature. 3. Water. 4. Soil. 

1. Importance of light. It is important for photosynthesis, flowering in plants, plant growth, metabolism, and periodicity.

2. Effect of temperature. It is the most important factor affecting almost all activities of organisms. 

3. Effect of Water- Water is essential for life. It covers more than 70% of the earth’s surface and forms the most extensive habitat for the organisms. Types of plants and animals distributed in water bodies greatly depends upon the nature of water (fresh-water or sea water). Land plants derive water from the soil while the land animals derive water from pools, ponds, lakes, rivers, springs etc.

4.Effect of Soil - Soil provides the necessary nutrition and minerals for the growth of plants and also provides shelter to anumber of organisms. 

Logistic population growth curve states that environment does not have unlimited resources and cannot permit exponential growth. In nature, a given habitat has resources to support a certain possible number, beyond which no further growth is possible. This limit is called as carrying capacity (K) for that species in that habitat.
A population growing in a habitat with limited resources shows initially a lag phase, followed by phases of increase and decrease and finally the population density reaches the carrying capacity. A plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called Verhulst-Pearl Logistic Growth as explained by the following equation:
                $\frac{\mathrm{dN}}{\mathrm{dt}} = \mathrm{rN}\left(\frac{\mathrm{K}-\mathrm{N}}{\mathrm{K}}\right)$

Logistic Population growth curve 

It shows the different phases of the Logistic growth
(i) Lag phase- during this period the population shows avery slow growth due to limited resources.
(ii) Acceleration phase where the population grows at a high rate due to availability of resources.
(iii) Decceleration phase where the population growth decreases due to less resources.
(iv) Steady state - when the growth stops and the population reaches its carrying capacity.

Adaptations in desert animals -:
Animals excete solid urine and faeces , possess spiny skin and highly cornified skin, they come out during the night or early morning for fedding purposes to prevent loss of water and the scorching heat of the desert.

(b) Adaptations of plants to water scarcity - Plants adapt to water scarcity by having
i. thick waxy coating or cuticle.
ii. sunken stomata
iii. extensive and highly branched root system.
iv. leaves reduced to spines and thick and fleshy stems.
v. By using the Cam pathway for the production of food.

(c) Behavioural adaptations in animals. The various behavioural adaptations in animals are
i. Migration
ii. Hibernation and aestivation.
iii. Certain animals change their feeding and foraging time and pattern.
iv. some animals like lizards(ectotherms) bask in the sun to absorb heat and moving to shade when the ambient temperature increases.

(d) Importance of light to plants-  
Light is the major and ultimate source of energy for plants. Plants use light to synthesize  food. The light also induces photoperiodic responses like it effects flowering in plants. The UV spectrum of the Light is very important for the plants in places where the light cannot reach.

(e) Effect of temperature and waters scarcity and the adaptaions of animals. 

Temperature plays and important role as it affects the kinetics of the enzymes and metabolism, activity and other physiological functions. It also affects the habitat, geographical distribution and pigmentation. The animals of the cold regions develop thick fur and have more fat so as to avoid the cold conditions. The animals which can bear a wide range of temperature have a more distributional range. Certain animals which cannot regulate the temperature for eg. desserts lizards bask in the sun to absorb heat and move to shade when the temperature increases.

Animals tend to adapt to the water scarcity by 
i. Exceting solid urine and faeces ,
ii. Having spiny skin and highly cornified skin, iii. Changing the feeding habits that is they come out during the night or early morning for fedding purposes to prevent loss of water .

Organisms living in polar regions have to face the severe winter and show different types of adaptations.
(i) They have thick fur and more amount of fat for insulation from the cold.

(ii) During extreme winter they undergo hibernation during which their metabolic activities slow down and they sleep for a long period to avoid the harsh cold condition.

(iii) They have shorter ears and limbs to minimise heat loss.

1.  Presence of thick cuticle on stem and leaf surfaces. This reduces the rate of transpiration.

2. Some desert plants develop succulent organs (stems, leaves and roots) e.g. Asparagus, Begonia, Bryophyllum.

3. Presence of extensive root system to absorb water.

4. Either leaves are absent or small-sized leaves or transformed into spines to minimize the rate of transpiration.

5. The stomata get sunken to reduce the rate of transpiration.

6. Some xerophytes remain dormant either as seeds or as roots and  they sprout up during rains e.g. Cassia, Argemone

(ii) Environmental resistance. The factors such as shortage of food, disease, predation, environmental natural calamities which impose a check on population size constitute environmental resistance. Environmental resistance decreases the rate of population growth.

(iii) Carrying capacity. It is a measure of the feeding capacity of an environment or ecosystem for a population of a species under a given set of conditions. If the population reaches its carrying capacity then the no further growth of the pooulation takes place.

Gause’s competitive exclusion principle states that two closely related species competing for the same resources cannot exist together indefinitely as the competitively inferior one will be eliminated eventually.

Mac Arthur had shown that five closely related species of warblers living on the same tree were able to avoid competition and co-exist to behavioural differences in their foraging activities. He gave an example of 'competitive release'.

D.

One organism is benefited, other is affected.

The age pyramid that reflects a stable growth status of human population can be represented as follows:

(i) Curve a represents exponential growth which shows that there is ample food and space for the population. Resources are unlimited.

Curve b represents logistic growth and shows that there is limiting food and space for the population. The resources are limiting.

(ii) In the absence of predators, curve (a) would appropriately depict the prey population.

(iii) The dotted line represents the carrying capacity of the environment. The carrying capacity represents the size of population that the environment can hold by providing necessary resources. When a population reaches this line its population size is stabilized by various environmental factors.

Analysis of age pyramids for human population can provide important inputs for long-term planning strategies. The different age groups present in a population determine its reproductive status. Distribution of age groups highly influences the growth of the population. Each population displays following three ecological ages or age groups:

1. Pre-reproductive 

2. Reproductive 

3. Post-reproductive 

Population having large number of young members grows rapidly, while, the population having more number of post-reproductive members tends to be declining. There are basically three types of age pyramids they are as follows:

Therefore, through the thorough analysis of the age pyramids of a particular population, the distribution of resources can be done more efficiently. A better planning strategy can be adopted considering the demand of the resource; thus, long-term management of resources can be done in such a way that the population can derive maximum benefit with minimum effects on nature, leading the population to flourish efficiently.

GPP – R = NPP (where GPP = Gross Primary Productivity, R = Respiratory losses and NPP = Net Primary Productivity)

Pyramid of energy is upright because when energy flows from a particular trophic level to next trophic level, some energy is always lost as heat at each step. So the energy in the subsequent trophic level is always less.

Mutualism is the interaction which confers benefits on both the interacting species.

For example:

i. Lichens represent an intimate mutualistic relationship between a fungus and photosynthesizing algae or cyanobacteria in which the fungus provides protection to the algae or cyanobacteria and the algae and cyanobacteria provide food to the fungus.

ii. Mycorrhizae are associations between fungi and roots of higher plants. 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.

In commensalism the interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism.

 Species            Species                 Name of interaction

A                             B

+                             +                            Mutualism

1. Bacteria forms thick-walled spores (cysts) unfavourable conditions and spores are shed on availability of suitable environment.

2. In higher plants, seeds remain dormant under unfavourable conditions and germinate under favourable moisture and temperature conditions.

3. Animals like bears undergo hibernation and suspend their metabolic activities to avoid the harsh winter conditions.

4. Under unfavourable conditions, many zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development.

(i) Ascaris worms living in the intestine of human -Parasitism

(ii) Wasp pollinating fig inflorescence - Mutualism

(iii) Clown fish living among the tentacles of sea-anemone - Commensalism

(iv) Mycorrhizae living on the roots of higher plants- Mutualism

(v) Orchid growing on a branch of a mango tree - Commensalism

(vi) Disappearance of smaller barnacles when Balanus dominated in the Coast of Scotland - Competition

Four techniques where the principle of ex-situ conservation of biodiversity has been employed are as follows:

i. Preservation of the gametes of threatened species (using cryopreservation techniques) in viable and fertile condition for long periods.
ii. In-vitrofertilisation of eggs.

iii. Tissue culture techniques used for the propagation of plants.
iv. Seed banks are used to keep the seeds of different genetic strains that are commercially important plants for long periods.

The various ways in which the animal adapt to unfavourable conditions are:

Snails undergo aestivation to avoid summer-related problems like excessive heat and desiccation.
Seeds go into a state of ‘dormancy’ in which they reduce their metabolic activities. They germinate when the conditions are again favourable.
Bears go into hibernation to avoid the harsh winter conditions in which they reduce their body metabolic activities to a great extent.
Zooplanktons undergo a state of ‘Diapause’ that is a stage of suspended development)

Fungi form thick-walled spores to survive the unfavourable conditions and germinate on the availability of suitable conditions.

(a) Following are the attributes that a population has but an individual organism does not have:

• Birth rate: per capita births. It represents the increase in number with respect to the population.
• Death rate: per capita deaths. It represents the decrease in number with respect to the population.
• Sex ratio: Ratio of number of males to females in a given  population.
• Age distribution: A population at any given time is composed of individuals of different ages.

(b) Population density means number of individuals present per unit area. Population density can be measured by determining the population size. The different methods to study population size are as follows:

(1) Indirect method:  In this method the population density is measured without actually counting or seeing the organism. For examples – the tiger consensus in our national park and tiger reserves are often based on the pug marks and fecal pellets of the tiger.
Example: The number of Parthenium plants in a given area can be measured using the quadrat method.

(2) Direct observation: It involves the counting of organisms in the given area.
Example: In order to determine the number of bacteria growing in a Petri dish, their colonies are counted.

Glomus forms Mycorrhizae with the higher plants and exhibits Mutualism.

The phenomenon of multiple allelism and co-dominance is shown by the ABO blood group in human beings. The gene I for the blood group contains three alleles i.e. I^A, I^B and i which represents the phenomenon of multiple allelism as it has more than two alleles governing the same character. The alleles I^A and I^B  are co-dominant and express themselves even in the presence of the other. Thus the presence of both the alleles I^A and I^B gives the blood group of AB.

The scientific name of the fruit-fly is - Drosophila melanogaster.

Morgan preferred to work with fruit-flies for his experiments because of the following reasons:

i. They could be grown on simple synthetic medium in the laboratory.

ii. They completed their life cycle in about two weeks and a single mating could produce a large number of progeny flies.

iii. It had many types of hereditary variations that could be seen with low power microscopes.

The fig tree and the wasp are onto a mutual relationship that shows the phenomenon of co-evolution. It mean that evolutions of the flower and its pollinator species are tightly linked with one another. The female wasps use the flower to lay egg and as a source of food for the larvae and pollinate the flowers in return.

Brood parasitism is a type of parasitism in birds in which the parasitic bird lays its eggs in the nest of its host and lets the host incubate them. For example, cuckoo (koel) lay its eggs in the nest of crow. During the course of evolution, the eggs of the parasitic bird have evolved to resemble the hosts egg in size and colour to reduce the chances of the host bird detecting the foreign eggs and ejecting them from the nest.

(a) Population density means number of individuals present per unit area. We can find out population density of a habitat by determining the population size. The different methods to study population size are as follows:-

(1) Total number: In this method the total number of organism in the population is counted. For example, in order to determine the number of bacteria growing in a Petri dish, their colonies are counted.

 (2) Relative densities- In this method relative density of the population is taken into account rather than counting the total number. For example - The number fish caught per trap gives the measure of their total population density in the given water body.

(3) Percent cover or biomass cover: For example in a population of 200 Parthenium plants and a single huge Banyan tree the percent cover of both are taken into account. 

(b) The study of population tells us a lot about the status of the species in the habitat. It tells us about -:

(i)The outcome of competition with another species.

(ii) The impact of a predator.

(iii) The effect of a pesticide application .

(a) Tourists visiting high altitude areas such as Rohtang Pass or Mansarovar, experience altitude sickness. Its symptoms include nausea, fatigue and heart palpitations. This is because in the low atmospheric pressure of high altitudes, the body does not get enough oxygen. But, gradually we get acclimatised and stop experiencing altitude sickness. The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of  hemoglobin and by increasing breathing rate. Thus, the visitors are advised to resume their normal active life involving heavy works only after few days because for doing heavy tasks our body needs energy and this energy is obtained by the oxidation of glucose in the presence of oxygen which is a limiting factor in higher altitudes.

(b) Smaller animals are rarely found in Polar Regions because small animals have a larger surface area relative to their volume. Since heat loss or heat gain is a function of

Parasitism - is a non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host. For example the relationship between the human liver fluke and its hosts that is the snail and a fish. 

In the case of co-evolutiion, the species interact so intimately that they can cause evolutionary changes in each other over time.The term coevolution is used to describe cases where two (or more) species reciprocally affect each other's evolution. So for example, an evolutionary change in the morphology of a plant, might affect the morphology of a herbivore that eats the plant, which in turn might affect the evolution of the plant, which might affect the evolution of the herbivore. For example, the Mediterranean orchid Ophrys bears flowers, the petals of which bear uncanny resemblance with the female bee. If there are any changes in the female bee's colour or pattern, the plant will also co-evolve to maintain the resemblance.

(a) Growth models
(1) Exponential growth - When the resources in the habitat are unlimited, each species has the ability to realise its innate potential t grow in number fully.
(2) Logistic growth - In nature, a given habitat has enough resources to support maximum possible number, beyond which no further growth is possible.
(b) 

Exponential growth	Logistic Growth
The graph is J-shaped.	The graph is Simoid shaped

(a) The symptoms of altitude sickness are fatigue and nausea.
(b) Altitude sickness is caused as the body does not get enough oxygen because of the low atmospheric pressure.
(c) After some time the body usually gets acclimatised. The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of haemoglobin and by increasing breathing rate.

(a) A population can be composed of individuals of different age groups. Age distribution plot for a given population is given by the age pyramid.

(b) The structure of the age pyramid determines the growth status of the population, that is, whether it is growing, stable or declining. On the basis of the collective information, the policies for the population can be decided. These may emphasis on providing food to the population, development of proper health services and much more.
For example, if the population is growing the policies can be made to increase the food resources to maintain the population. 
If the population is declining then the policies can be made to keep a check on the mortality rate of the population. 

The three features for plants and animals which enable them to survive in water scarce environment are:
i. The plants carry out the CAM cycle and the animals tend to be nocturnal and come out at night. 
ii. The plants have leaves reduced to spine to reduce the surface area and prevent loss of water. The animals have dry scaly skin.
iii. Plants have sunken stomata. Animals go into aestivation to escape the harsh condition.

The organisms cope up with the localised or short duration stressful conditions in the following ways:
Plants undergo dormancy and germinate on the availability of suitable conditions. The seeds and some other vegetative structures serve as means to tide over the period of harsh conditions and germinate under the favourable condition when the temperature and moisture are adequate.
Animals either migrate to some other place where the environmental conditions are favourable, or they go into aestivation or hibernation. The zooplankton enters into the state of diapause. All these stages show minimal metabolic activity and suspended development. 

Carrying Capacity

Ernst Munch

(a) 'Regulators' : - The organism is able to maintain homeostasis by physiological and behavioural means. All birds and mammals and few lower vertebrates and invertebrates species maintain homeostasis by thermoregulation and osmoregulation. For eg : - Birds & Mammals. 'Conformers' : - Majority (99%) of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature is not constant. They are simply conformers. Eg; - Fishes, Frogs etc.
(b) Because they lack the capability maintain a constant internal environment or homeostasis.

The rate of biomass production per unit area, over a time period by plant during photosynthesis is called productivity. * It is expressed in (kcal m–2)yr–1 or g/m2 / yr or g m–2 y –1.* The amount of biomass or organic matter produced per unit area over a time period in plants during photosynthesis is called primary production.

(a) There are 2 models of population growth : (i) The exponential growth (ii) Logistic growth (i) Exponential growth : This growth occurs where the resources (food + space) are unlimited. The equation can be represented as dt dN = (b – d) × N Let (b – d) = r rN dt dN = or rt t 0 N = N e N = population size Nt = population density after time t. N0 = population density at time zero r = growth rate b = birth rate d = death rate In this growth, when N in relation to time is plotted on graph, the curve becomes J-shaped.


(a) J-shaped curve ⇒ exponential growth
(b) S-shaped curve ⇒ logistics growth
Every ecosystem has limited resources to support a particular maximum carrying capacity (K). When N is plotted in relation to time t, a sigmoid-S-shaped curve is obtained & is also called as VERHULST-PEARL logistic growth. The equation is : dt dN = rN K (K − N) N = population density at time t. r = growth rate K = carrying capacity.

Regulate: Some organisms are able to maintain homeostasis by regulating their body temperatures. The mechanisms used by most mammals to regulate their body temperature are similar to what we humans use.

Eg: Body temperature remains constant at 37⁰C. In summer, when outside temperature is more than our body temperature, we sweat profusely and when the temperature is much lower than 37⁰C, we shiver thus body temperature remains constant.

(ii) Conform :Many animals, cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. These are conformers. Heat loss or heat gain is a function of
surface area. Since small animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside. Eg. Shrews and hummingbirds.

(iii) Migrate: The organism can move away temporarily from the stressful habitat to a more hospitable area & return when stressful period is over.
Eg: Every winter, the famous Keoladeo National Park in Bharatpur host thousands of migratory birds coming from Siberia & other northern regions.

(iv) Suspend: In animals, if migration is not possible, they might avoid the stress by escaping in time.
Eg: (1) Bears go into hibernation during winter.
(2) Fishes go into aestivation to avoid summer related problems heat & desiccation.

Deat Rate: Number of deaths per 1000 individuals of a population

Death Rate = 8/80 = 0.1

A.

smaller animals have a higher metabolic rate

Basal metabolic rate is inversely proportional to body size. So smaller animals have a higher metabolic rate, thus have quick and more energy required to go up the hills. 

D.

when N/K is exactly 1

In logistic growth model population growth equation is described as

where,
N = Population density at time t
r = Intrinsic rate of natural increase
K = Carrying capacity
When, N/K = 1 then

B.

No two species can occupy the same niche indefinitely for the same limiting resources

Gause's principle of competitive exclusion states that no species can occupy the same niche indefinitely for the same limiting resources.

C.

number of annual rings

Age of tree can be estimated by a number of annual rings. The two kinds of woods that appear as alternate concentric rings; constitute an annual ring heartwood comprises dead elements with highly lignified walls that give mechanical support to the steam. The height and girth of a tree increase due to the activity of vascular cambium.

B.

Biotic community

An association of individuals of different species living in the same habitat and having functional interaction is called biotic community (biocoenosis). The biotic community is dominated by one of the character. It determines the nature of community. It can be biotic or abiotic. 

B.

vacuoles

A.

Competition

Competition is a negative interaction that occurs among organisms whenever two or more organisms require the same limited resource. 
                           Population Interactions
Species A          Species B               Name of interaction
+                          +                            Mutualism
-                           -                             Competition
+                          -                             Predation
+                          -                             Parasitism

B.

population B competed more successfully for food than population A

The individuals of population-B have increased because they have adapted better to their environment then population-A.
Population-B had proved to be superiority adopted for survival and attainment of resources like food, water, shelter etc. leading to an increase in their number by outgrowing the offsprings, as compared to those of population-A.

A.

I and III

Some organisms show behavioural responses to cope with variations in their environment. Desert lizzards bask in the sun and absorb heat when their body temperature drops below the comfort zone, but move into shade when the ambient temperature starts increasing. Some species are capable of burrowing into the soil to hide and escape from the above-ground heat.

B.

Head louse living on the human scalp as well as laying eggs on human hair

Human louse (pediculus) lives among hair and surface of human body feeding on blood. It spreads diseases like typhus.

B.

Declining Population

An age pyramid is a graphic representation of the proportion of various age groups of a population with pre-reproductive at the reproduction in the middle and posts-reproductive at the top. For human population, the age pyramids show age distribution of males and females in the combined diagram. The shape of the age pyramids reflects the growth status of the population. In a declining population the shape of the pyramid is urn- shaped.

D.

(1) hibernation, (2) escape, (3) expanding, (5) hot spot

Bears go into hibernation during winter t o escape the cold weather. 
A conical age pyramid with a broad base represents expanding the human population.
A wasp pollinating a fig flower is an example of mutualism.
An area with high levels of species richness is known as hot spots.

D.

a) Regulator - mammals and birds
b) Conformer - all plants and 99% animals
c) Partial regulators - 

A.

eubacteria and archaea

Thermophiles live in hot places, typically from 60^o to 80^oC. Many thermophiles (some eubacteria and archaebacteria) are autotrophs and have metabolisms based on sulphur. Some thermophilic archaebacteria form the basis of food webs around deep- sea thermal vents, where they must withstand extreme temperature and pressure. Archaebacteria can grow in highly acidic (pH = 0.7) and very basic (pH= 11) environments.

D.

It has more cytoplasm and more DNA than an uncleaved zygote

Cleavage divisions are mitotic division, in which the single -celled zygote is converted into a multicellular morula. But during cleavage divisions, there is no growth of resultant daughter cells/blastomeres. So, the DNA content will increase, but there is no increase or insignificant increase in amount of protoplasm.

C.

Predator is an organism that catches and kills other organism for food

A.

'A' is more recent and shows slight reduction in the growth rate

Interpretation 'A' is correct for the given figures.

C.

d

Habitat is the place where an organism live. The population has been defined as a collective group of organisms of the same species occupying a particular place at a particular time. In the given table area d has maximum species diversity, as there are 10 species (A-J) reside in 12 habitats, while in area c the 10 species reside in 13 habitats so, exhibit less diversity than area d.

B.

Hereditary diseases like colour blindness do not spread in the isolated population

The population can be defined as a group or assemblage of organisms of the same species that live at a given time in a particular area. In human beings a dominant X- linked gene is necessary for the formation of colour sensitive cells the cones, in the retina of the eye. The recessive form of this gene is incapable of producing the colour sensitive cones and homozygous recessive female and hemizygous recessive males are unable to distinguish between these two colours. As the isolated population do not have any hereditary diseases like colour blindness, so they do not spread accordingly.
According to the theory of inheritance of acquired characters of Lamarck the Wrestlers, who develop strong body muscles in their lifetime, must pass this character onto their progeny, but this is not found true.
Gene pool is defined as the sum total of genes present in a Mendelian population. The study of gene pools tells us the total number of genes, their kinds and variety present in the population.

A.

B and C

The series of organisms eating one and being eaten by other is called food chain. A simple food chain consists of producers, herbivores and carnivores. The length of the food chain is generally limited to 3-4 trophic levels due to energy loss. In grazing food chain the producers (ie, plants) are eaten by herbivores are eaten by carnivores. Therefore, the removal of most of the carnivores resulted in an increased population of deer.

C.

Its population growth curve is of J-type

Its population growth curve is J-shaped in which density increases rapidly in exponential fashion and then stops abruptly as environmental resistance or another limiting factor becomes effective more or less suddenly.

B.

Population

Geometric representation of age structure is a characteristic of population. In most-populations, individuals are of different ages. The proportion of individual in each age group is called age structure of that population.