🌸Chapter 11
Organisms & Populations
(4 Marks)
1.
Explain
the concept of population and its characteristics.
Answer:
- Population: Group of individuals of the
same species living in a particular area at a given time.
- Characteristics:
- Size: Total number of individuals.
- Density: Number per unit area/volume.
- Dispersion: Spatial distribution
(clumped, uniform, random).
- Age structure: Distribution among
pre-reproductive, reproductive, post-reproductive groups.
2.
Explain
three types of population dispersion with suitable examples.
Answer:
- Clumped: Individuals in groups; elephants,
schooling fish.
- Uniform: Evenly spaced; penguins,
territorial birds.
- Random: Unpredictable; dandelions,
trees in forests with uniform resources.
3.
Differentiate
between natality and mortality and explain their effect on population.
Answer:
| Feature | Natality | Mortality |
|-------------|-------------------------|-------------------------|
| Meaning | Birth rate | Death rate |
| Effect on population | Increases population size | Decreases population size
|
- Population growth depends on the balance of natality
and mortality.
4.
Explain
intraspecific and interspecific competition with examples.
Answer:
- Intraspecific: Competition among same
species; e.g., trees of same species competing for sunlight.
- Interspecific: Competition among different
species; e.g., lion and hyena competing for prey.
- Both regulate population
size and resources in an ecosystem.
5.
Explain
carrying capacity and factors affecting it.
Answer:
- Carrying capacity (K): Maximum population an
environment can sustain indefinitely.
- Factors affecting K:
- Food, water, shelter
availability
- Predation
- Disease
- Environmental conditions
6.
Explain
the exponential (J-shaped) and logistic (S-shaped) population growth curves.
Answer:
- Exponential growth:
- Unlimited resources, no
environmental resistance
- Rapid growth (J-shaped curve)
- Logistic growth:
- Growth slows as population
approaches carrying capacity
- S-shaped curve
- Density-dependent regulation
7.
Describe
the three phases of population growth.
Answer:
- Lag phase: Slow growth, population
adjusting.
- Log (exponential) phase: Rapid growth due to abundant
resources.
- Stationary phase: Growth stabilizes at carrying
capacity due to limited resources.
8.
Explain
the importance of studying population age structure.
Answer:
- Predicts future population
trends
- Broad pre-reproductive → population
expansion
- Broad post-reproductive →
population decline
- Helps in policy-making,
resource planning, and conservation strategies
9.
Explain
the concept of ecological niche with examples.
Answer:
- Niche: Functional role of species in
ecosystem (habitat, food, interactions).
- Examples:
- Honeybee: Pollinator, feeds on
nectar
- Lichen: Alga + fungus
mutualism
10.
Explain
mutualism and give two examples each from plants and animals.
Answer:
- Mutualism: Both species benefit.
- Plant examples: Lichen (alga + fungus),
mycorrhizal associations
- Animal examples: Oxpecker and rhinoceros,
clownfish and sea anemone
11.
Explain
commensalism with examples.
Answer:
- One species benefits, the other
unaffected.
- Plant example: Epiphytic orchids on trees
- Animal example: Cattle egret and cattle
12.
Explain
parasitism with examples in plants and animals.
Answer:
- One species benefits at the
expense of the host.
- Plant example: Cuscuta on host plants
- Animal example: Tick on dog
13.
Explain
amensalism with examples.
Answer:
- One species is harmed, the
other unaffected.
- Example: Penicillium secreting
antibiotic affecting bacteria; elephant stepping on ants.
14.
Explain
predation and its ecological significance.
Answer:
- Predator feeds on prey to
survive.
- Example: Lion hunting deer
- Significance:
- Controls prey population
- Maintains ecosystem balance
- Drives natural selection
15.
Differentiate
between density-dependent and density-independent factors.
Answer:
| Feature | Density-Dependent | Density-Independent |
|--------------------------|---------------------------|---------------------------|
| Effect based on density | Increases with density | Independent of density |
| Examples | Disease, competition, predation | Flood, fire, earthquake |
16.
Explain
the formula ΔN = (B–D) + (I–E) with example.
Answer:
- ΔN = Change in population size
- B = Births, D = Deaths, I =
Immigration, E = Emigration
- Example: 100 births, 40 deaths,
20 immigration, 10 emigration → ΔN = (100–40) + (20–10) = 70
17.
Explain
clumped dispersion in animals and its adaptive significance.
Answer:
- Individuals occur in groups;
e.g., elephants, fishes.
- Significance: Protection, social
interaction, better resource access, mating efficiency
18.
Explain
uniform dispersion and give an example.
Answer:
- Individuals evenly spaced due
to competition or territoriality.
- Example: Penguins in breeding colonies
19.
Explain
random dispersion and give an example.
Answer:
- Individuals distributed
unpredictably due to uniform resources and lack of strong interactions.
- Example: Dandelions in a field
20.
Explain
how immigration and emigration affect population size.
Answer:
- Immigration increases
population size; emigration decreases it.
- Influences density, growth
rate, and genetic diversity.
21.
Explain
why age pyramids are important in human population studies.
Answer:
- Predict population growth
trends
- Plan resources like food,
schools, employment
- Identify future challenges in
healthcare and economy
22.
Explain
morphological, physiological, and behavioral adaptations with examples.
Answer:
- Morphological: Thorns of cactus
- Physiological: Camel hump
storing fat
- Behavioral: Nocturnal activity
of desert animals
23.
Explain
why population growth cannot continue indefinitely.
Answer:
- Limited resources (food, space,
water)
- Predation, disease, competition
- Population stabilizes near
carrying capacity
24.
Explain
the ecological significance of parasitism.
Answer:
- Regulates host population
- Drives natural selection
- Maintains ecosystem stability
25.
Explain
the role of competition in population regulation.
Answer:
- Reduces overpopulation
- Ensures survival of fittest
- Maintains balance in ecosystems
26.
Explain
the adaptive significance of nocturnal behavior in desert animals.
Answer:
- Avoids daytime heat, reduces
water loss
- Enhances survival under harsh
conditions
27.
Explain
why broad-based age pyramids indicate expanding populations.
Answer:
- High proportion of young
individuals → high reproductive potential → rapid population growth
28.
Explain
why narrow-based age pyramids indicate declining populations.
Answer:
- Few young individuals → low
reproductive potential → decreasing population size
29.
Explain
the significance of population density.
Answer:
- Helps measure resource use and
competition
- Indicates health of population
- Useful for conservation and
management
30.
Explain
the significance of studying population growth curves.
Answer:
- Predict population trends
- Plan conservation measures
- Understand environmental
effects and limiting factors
31.
Explain
the difference between population density and population size.
Answer:
- Density: Individuals per unit area
- Size: Total number of individuals in
an area
32.
Explain
pre-reproductive, reproductive, and post-reproductive age groups with examples.
Answer:
- Pre-reproductive: Children →
future growth
- Reproductive: Adults →
contribute to growth
- Post-reproductive: Elderly →
consume resources, no reproduction
33.
Explain
the role of predation in prey adaptations.
Answer:
- Drives evolution of defense
mechanisms: camouflage, speed, warning colors
- Maintains predator-prey balance
34.
Explain
exponential growth with example.
Answer:
- Rapid, J-shaped growth under
unlimited resources
- Example: Bacteria in
nutrient-rich medium
35.
Explain
logistic growth with example.
Answer:
- S-shaped growth, slows near
carrying capacity
- Example: Deer in forest limited
by food
36.
Explain
intraspecific competition with example.
Answer:
- Competition among same species
for resources
- Example: Trees of same species
competing for sunlight
37.
Explain
interspecific competition with example.
Answer:
- Competition among different
species
- Example: Lion and hyena
competing for prey
38.
Explain
density-independent regulation with example.
Answer:
- Population affected regardless
of density
- Example: Flood, fire
39.
Explain
density-dependent regulation with example.
Answer:
- Effect increases with density
- Example: Disease spreads faster
in crowded rabbits
40.
Explain
the concept of ecological niche with animal example.
Answer:
- Functional role of species in
ecosystem
- Example: Honeybee – pollinator,
nectar feeder
41.
Explain
how predation influences population dynamics.
Answer:
- Reduces prey numbers
- Influences prey adaptations
- Maintains ecosystem stability
42.
Explain
why logistic growth is density-dependent.
Answer:
- Growth slows as population
nears carrying capacity
- Factors like competition,
disease, and predation limit population
43.
Explain
the importance of studying population ecology in conservation.
Answer:
- Helps maintain biodiversity
- Predicts population trends
- Aids in resource management and
sustainable use
44.
Explain
the role of limiting factors in population regulation.
Answer:
- Resources, predation, disease
limit growth
- Ensure population does not
exceed carrying capacity
45.
Explain
the concept of zero population growth.
Answer:
- Birth rate = death rate
- Population size remains
constant
- Common in developed countries
46.
Explain
the relationship between population size and carrying capacity.
Answer:
- When population < K → growth
positive
- Population = K → growth
stabilizes
- Population > K → resources
insufficient → population declines
47.
Explain
the ecological significance of age structure in population management.
Answer:
- Helps in planning resources
- Predicts future population size
and growth trends
48.
Explain
the effect of human activities on population dynamics.
Answer:
- Habitat destruction, pollution,
hunting affect size and growth
- Alters age structure, dispersion,
and carrying capacity
49.
Explain
the significance of studying dispersion patterns in ecology.
Answer:
- Helps understand social
behavior, resource distribution, competition
- Guides conservation and
management strategies
50.
Explain
the adaptive significance of morphological, physiological, and behavioral
traits in population survival.
Answer:
- Morphological: Protection and
survival (thorns)
- Physiological: Internal
survival mechanism (camel hump)
- Behavioral: Activity patterns
for survival (nocturnal activity)
