B4.2 ECOLOGICAL NICHES

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29 Terms

1
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Define a niche.

A niche is the role of an organism in its environment, including its habitat, feeding, and interactions with other species.

2
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Define a habitat.

The habitat is the physical environment in which a species, population, or community normally lives.

3
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Distinguish between habitat and niche.

A habitat is the physical space, while a niche includes the organism's role, diet, and relationships.

4
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Define a fundamental niche.

The potential mode of existence of a species, assuming no competition.

5
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Define a realized niche.

The actual mode of existence, considering interactions such as competition and predation.

6
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Compare fundamental and realized niches.

Realized niches are always equal to or smaller than fundamental niches due to biotic pressures like competition.

7
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State the competitive exclusion principle.

Two species cannot occupy the same niche indefinitely; one will eventually outcompete and exclude the other.

8
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Explain why two species cannot share the same niche.

They would compete for the exact same resources. One would dominate, causing the other to either adapt, migrate, or go extinct.

9
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Provide an example of competitive exclusion.

Oak vs. Birch: Both compete for sunlight and nutrients. Oaks grow taller and eventually block light, causing birch trees to die.

10
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Define holozoic nutrition.

Ingestion of whole organisms or parts, followed by digestion and absorption (e.g., humans).

11
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Outline saprotrophic nutrition.

Organisms secrete enzymes onto dead organic matter and absorb nutrients externally (e.g., fungi, bacteria).

12
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Distinguish between saprotrophs and detritivores.

Saprotrophs digest outside the body; detritivores ingest first and digest internally.

13
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State one example of a mixotroph.

Euglena: photosynthesizes and also feeds on organic matter.

14
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Define obligate aerobes.

Require continuous oxygen for survival (e.g., most eukaryotes).

15
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Define obligate anaerobes.

Cannot survive in oxygen-rich environments (e.g., some archaea).

16
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Define facultative anaerobes.

Can live in both oxic and anoxic conditions (e.g., yeast).

17
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Describe 3 physical adaptations of herbivores.

1) Dental pad (no upper incisors)

2) Broad molars for grinding

3) Chisel-like teeth for gnawing

18
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Outline 2 digestive adaptations in herbivores.

1) Four-chambered stomach for microbial fermentation\

2) Alkaline saliva delays digestion and supports fermentation

19
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List physical predator adaptations.

Sharp claws, good eyesight, strong jaws

20
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Give two chemical predator adaptations.

1) Snakes and spiders produce venom/toxins

2) Use of chemical cues to locate prey

21
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Give an example of a behavioural adaptation in predators.

Use of calls or scents to coordinate group hunting

22
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Describe how height helps plants compete for light.

Tall plants reach the canopy, gaining better access to sunlight.

23
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Describe the function of lianas.

Lianas climb on other plants to access light without investing in thick stems.

24
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Explain the advantage of being an epiphyte.

Epiphytes grow on trees to reach sunlight, avoiding competition on the forest floor.

25
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Outline adaptations of shade-tolerant plants (5)

1) Broader/thinner leaves

2) Efficient use of far-red light

3) Chloroplast movement

4) Leaf repositioning

5) Slower, efficient nutrient use

26
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Describe the role of leaf surface area in light capture.

Large, thin leaves increase the light absorption capacity, especially in shady environments.

27
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Define competitive exclusion

Two species can not occupy the same niche because one will come to dominate and exclude the other.

28
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State why organisms in extreme niches face less competition.

Fewer organisms can survive in extreme conditions, so competition and predation are reduced.

29
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Give an example of an extremophile.

Thermophilic bacteria in hot springs