B4.2 - Ecological Niches

Question 1

What is an ecological niche?

Answer 1

The role a species plays in its habitat, including what it eats, where it lives, when it’s active, how it interacts with others, and what conditions it tolerates.

Question 2

What happens when two species occupy the exact same niche?

Answer 2

Competition occurs, and one species will exclude the other — this is called competitive exclusion.

Question 3

What are obligate anaerobes?

Answer 3

Organisms that can only survive in environments without oxygen, such as deep water, soil, and animal guts.

Question 4

What are facultative anaerobes?

Answer 4

Organisms that can switch between aerobic and anaerobic respiration depending on oxygen availability.

Example: E. coli.

Question 5

What are obligate aerobes?

Answer 5

Organisms that require oxygen and cannot survive without it.

Question 6

What are photoautotrophs?

Answer 6

Organisms that use light energy to convert CO₂ into organic molecules using chlorophyll.

Question 7

What organisms perform photosynthesis?

Answer 7

Plants, algae, and photosynthetic protists.

Question 8

What do photosynthetic organisms release and what does it enable?

Answer 8

They release oxygen, which enables aerobic respiration.

Question 9

What is heterotrophic nutrition?

Answer 9

Nutrition by ingestion: food is ingested, digested, and absorbed internally. Used by all animals.

Question 10

What’s the difference between internal and external digestion?

Answer 10

Internal digestion occurs inside the body (animals); external digestion happens outside (e.g., fungi).

Question 11

What is mixotrophic nutrition?

Answer 11

Nutrition using both autotrophic and heterotrophic methods.

Question 12

What are obligate mixotrophs?

Answer 12

Organisms that must use both autotrophic and heterotrophic nutrition.

Question 13

What are facultative mixotrophs? + example

Answer 13

Organisms that can switch methods depending on the environment.

Example: Euglena photosynthesizes in light and becomes heterotrophic when it’s dark or food is available.

Question 14

What is saprotrophic nutrition?

Answer 14

External digestion of dead matter using enzymes, followed by absorption of nutrients. Found in fungi and bacteria.

Question 15

What do saprotrophs leave behind?

Answer 15

Minerals and ions in soil — essential for plant growth.

Question 16

What types of nutrition are found in archaea?

Answer 16

Heterotrophic, phototrophic, and chemotrophic.

Question 17

What is the competitive exclusion principle?

Answer 17

Two species can’t coexist in the same niche forever. One will eventually outcompete the other.

Question 18

What is an example of competitive exclusion?

Answer 18

Paramecium aurelia outcompetes Paramecium caudatum when cultured together.

Question 19

What can competitive exclusion lead to?

Answer 19

Local extinction, resource partitioning, or niche differentiation.

Question 20

How is dentition adapted to diet in Hominidae?

Answer 20

Chimps have long canines (for meat), small incisors, and small jaw muscles.

Gorillas have large molars for grinding, strong jaw muscles for tough vegetation.

Question 21

What do fossils like Paranthropus and Homo floresiensis show?

Answer 21

Paranthropus robustus: robust skull, thick enamel, large molars → tough vegetation.

Homo floresiensis: square jaws, large premolars → plant-based diet.

Question 22

What are herbivory adaptations in insects?

Answer 22

Aphids: tube-shaped mouthparts (stylets) that suck sap.

Caterpillars: chew leaves with mandibles.

Question 23

What are herbivory adaptations in mammals?

Answer 23

Flat molars for grinding and saliva to neutralise toxins in stomach.

Question 24

What are mechanical plant defences?

Answer 24

Spines, hairs, thick bark.

Question 25

What are chemical plant defences?

Answer 25

Bitter tastes or toxins (e.g., tannins from acacia, caffeine from coffee, nicotine from tobacco).

Question 26

What are predator adaptations?

Answer 26

Chemical: venom, paralytic toxins (e.g., snakes, spiders). ## Footnote Physical: sharp claws, teeth, speed (e.g., cheetahs). ## Footnote Behavioural: ambush (e.g., leopards), teamwork (e.g., wolves).

Question 27

What are prey adaptations?

Answer 27

Chemical: toxins (e.g., dart frogs), bad taste. ## Footnote Physical: camouflage, armour (e.g., turtles). ## Footnote Behavioural: fleeing, playing dead, herding.

Question 28

How do rainforest plants adapt to access light?

Answer 28

Tall trees compete in canopy. ## Footnote Lianas (vines) climb trunks. ## Footnote Epiphytes grow on others for light. ## Footnote Strangler epiphytes climb then kill host trees.

Question 29

What are shade-tolerant shrub adaptations?

Answer 29

Thrive on forest floor using pigments like anthocyanins. ## Footnote Bright flowers to attract pollinators in low light.

Question 30

What is a fundamental niche?

Answer 30

The full potential range a species could occupy under ideal conditions (no competition).

Question 31

What is a realised niche?

Answer 31

The actual range a species occupies due to competition or environmental pressures.

Question 32

What is an example of fundamental vs. realised niche?

Answer 32

Chthamalus barnacles can live throughout the intertidal zone (fundamental), but are pushed higher by Balanus (realised).