B4.2 Ecological Niches

Question 1

What is an ecological niche?

Answer 1

The unique role a species fulfils in a community. This includes: its spatial habitat, how other organisms contribute to its growth and survival, and mode of nutrition.

Question 2

True or false?
Two species can occupy exactly the same niche within a habitat.

Answer 2

False, one species will always out-compete the other.

Question 3

What are obligate anaerobes?

Answer 3

Single-celled organisms that can only carry out anaerobic respiration (can’t tolerate oxygen). Eg. early bacteria

Question 4

Where can obligate anaerobes be found?

Answer 4

In oxygen free environments like:
- Lower layers of soil
- Deep sea
- Inside bodies of other organisms

Question 5

What are facultative anaerobes?

Answer 5

Organisms that mainly respire aerobically, but can switch to fully anaerobic respiration without negative effects.

Question 6

What are organisms that cannot survive in the absence of oxygen called?

Answer 6

Obligate aerobes (eg. most animals)

Question 7

What happens if obligate aerobes perform anaerobic respiration?

Answer 7

They will need to switch back to aerobic respiration after a few seconds, due to the damaging effects on cells.

Question 8

What is meant by “modes of nutrition”?

Answer 8

An organisms mode of nutrition is the way in which it acquires organic molecules to fuel respiration.

Question 9

Define heterotroph (a mode of nutrition)

Answer 9

Obtains organic compounds by consuming other organisms externally or internally.

Question 10

What is holozoic nutrition?

Answer 10

A form of heterotrophy where organisms ingest + internally digest + absorb + assimilate organic molecules.

Question 11

What is saprotrophic nutrition?

Answer 11

A type of heterotrophy where organisms secrete enzymes onto dead organic matter so digestion happens externally (aka decomposers).

Question 12

Name two examples of saprotrophs.

Answer 12

Bacteria and fungi

Question 13

Are all animals heterotrophic?

Answer 13

Yes

Question 14

What is an autotroph?

Answer 14

Organisms that synthesise organic compounds from inorganic molecules.

Question 15

What is a mixotroph?

Answer 15

Performs both autotrophic and holozoic nutrition depending on availability.

Question 16

Give an example of a mixotrophic organism?

Answer 16

Euglena –> freshwater protist that uses both photosynthesis + ingestion and digestion of bacterial cells.

Question 17

What is the difference between obligate and facultative mixotrophs?

Answer 17

Obligate = must constantly use both methods.
Facultative = can survive on one mode of nutrition, which may be supplemented by the other. Can switch.

Question 18

What are archaea?

Answer 18

A group of unicellular organisms that make up one of 3 domains.

Question 19

Archaea are metabolically very diverse. What are the 3 ways they provide energy for ATP production?

Answer 19

1. Light (photoautotrophic)
2. Oxidation of inorganic phosphate (chemoautotrophic)
3. Oxidation of carbon compounds (heterotrophic)

Question 20

What can infer from the dentition of Hominidae species?

Answer 20

Their diet

Question 21

Why do teeth not provide a perfect indication of the diets of extinct hominids?

Answer 21

Eating would not have been the only role played by teeth; they may also have been involved with, e.g. defending territory.

Question 22

What are the general features of teeth for herbivores?

Answer 22

1. Large, flat, broad molars to grind plants
2. Large jaw
3. Reduced canines (smaller and less sharp, more for intimidating)

Question 23

What are general features of teeth for omnivores?

Answer 23

1. Mixed teeth types (incisors, canines, molars)
2. Moderate jaw strength (softer foods)

Question 24

What are the two main groups of herbivores?

Answer 24

Chewing and sap-feeding herbivores

Question 25

What is an example of a sap-feeding herbivore?

Answer 25

Aphids

Question 26

How are insect mouthparts adapted for sap-feeding?

Answer 26

Tubular mouthparts that pierce plant tissues to reach phloem sieve tubes and sap.

Question 27

Give an example of a chewing herbivore

Answer 27

Beetles

Question 28

How are the mouthparts of chewing herbivores adapted?

Answer 28

Jaw-like mouth (mandible) for biting off, chewing, and ingesting leaf parts.

Question 29

Give an example of plant adaptations to deter herbivores

Answer 29

Mechanical defences: - Thorns (eg. cacti) - Stings (eg. nettles) - Thick bark Toxic secondary components: - Toxic, or taste bitter

Question 30

What are the 3 types of adaptations predators can have?

Answer 30

Physical Chemical Behavioural

Question 31

What is an example of a chemical adaptation in predators?

Answer 31

- Venoms - Chemical mimicry (eg. release hormones used by animal for mating to attract them)

Question 32

What are examples of physical adaptations that help predators catch prey?

Answer 32

- Long distance vision - Eyes on the front of their head (good distance perception) - Ability to run/swim/fly fast - Echolocation - Sharp claws

Question 33

What are some examples of behavioural adaptations used by predators?

Answer 33

- Pack hunting - Persistent hunting (tiring out prey) - Lying in wait

Question 34

Chemical adaptations of prey?

Answer 34

- Produce toxins that deter predators (eg. skunks and poison dart frogs) - Scent camouflage

Question 35

Physical adaptations of prey?

Answer 35

- Camouflage - Eyes on side of skulls for a wide field of view

Question 36

Behavioural adaptations of prey?

Answer 36

- Preference for dark, sheltered places - Moving away when detecting predators - Rolling into a ball - Group together - Playing dead

Question 37

What are some examples of plant adaptations for harvesting light?

Answer 37

- Trees that grow tall to reach the canopy - Using other plants as a support to reach the canopy, e.g. lianas, epiphytes and strangler epiphytes - Being shade-tolerant

Question 38

How do strangler epiphytes differ from lianas?

Answer 38

- Lianas germinate on the forest floor. - Strangler epiphytes begin their life in the canopy and grow both upwards and downwards to access resources.

Question 39

True or False? Shade-tolerant plants contain the same photosynthetic pigments as plants in the canopy.

Answer 39

False. Shade-tolerant plants often contain different photosynthetic pigments to absorb the limited light wavelengths that reach the forest floor.

Question 40

Why do ground-dwelling forest plants often have large leaves?

Answer 40

To maximise the surface area available for light absorption.

Question 41

What is the difference between a species' fundamental niche and its realised niche?

Answer 41

Fundamental niche: the niche that it has the potential to fill if there were no limiting factors. Realised niche: the niche a species actually occupies, in the presence of competitor species.