Impacts of biotic factors in ecosystems

Question 1

What is a population?

Answer 1

A group of organisms from the same species occupying in the same geographical area.

Question 2

Why can populations be difficult to define?

Answer 2

A population may comprise widely dispersed individuals which come together only infrequently, e.g. for mating.
Populations may fluctuate considerably over time.

Question 3

What are the main features of a population?

Answer 3

Population size: the total number of organisms in the population.
Population density: the number of organisms per unit area.
Population distribution: the location of individuals within a specific area.

Question 4

How can environmental factors be organised?

Answer 4

How much population density influences their effect on population growth

Question 5

What are density independent factors?

Answer 5

They have a controlling effect on population size and growth, regardless of the population density. Include temp. humidity, rainfall, but also events including droughts and floods.

Question 6

What are density dependent factors?

Answer 6

They exert a greater effect on population growth at higher population densities. At high densities, individuals
compete more for resources, are more easily located by predators and parasites, are more vulnerable to infection and disease. Include food supply, competition and parasites.

Question 7

What is predation?

Answer 7

A type of feeding relationship where the predator obtains food by killing and eating another animal.

Question 8

Provide some example of predator prey relationships.

Answer 8

Spider traps fly in its web.

Carnivorous plants catch insects for extra nutrients.

Question 9

What is competition?

Answer 9

Both organisms are harmed in a relationship where they try to obtain a shared but scarce resource such as food, shelter and mates. Reward of resource outweighs risk of the interaction.

Question 10

What is infraspecific competition?

Answer 10

Competition between members of a species - more intense as they have more resources needs in common.

Question 11

Provide an example of infraspecific competition.

Answer 11

Red kangaroos fight for female reproductive partners.

Question 12

What is interspecific competition?

Answer 12

Competition between members of different species. Can lead to the evolution of one species in response to the selection pressure exerted by the other species that alters its niche.

Question 13

Provide an example of interspecific competition.

Answer 13

In Britain, introduction of the larger, more aggressive, American grey squirrel in 1846 was followed by a steady contraction in the range of the native red squirrel.

Question 14

What is the main way that plants engage in competition?

Answer 14

They perform allelopathy, the production of specific chemicals by a plant to either benefit or harm nearby plants.

Question 15

What is the aim of plants engaging in allelopathy?

Answer 15

Chemicals produced by one plant with inhibit the growth of other plants nearby, keeping them away. This means the plant has more available water, soil, nutrients and sunlight.

Question 16

Describe some forms of allelopathy.

Answer 16

Chemicals are used to inhibit shoot/root growth, seed germination, respiration, photosynthesis, nutrient uptake, alter chlorophyll levels.

Question 17

Provide examples of allelopathy.

Answer 17

Pines tree needles release acid into the soil, inhibiting other plants from growing nearby.
Fungi produce antibiotics to inhibit the growth of bacteria.

Question 18

What is symbiosis?

Answer 18

Interactions between two organisms where at least one benefits. Involves providing food, cleaning, or transportation.

Question 19

What is obligate symbiosis?

Answer 19

One or both species completely rely on the other for survival.

Question 20

What is facultative symbiosis?

Answer 20

The organisms can live independently but engage in the relationship for benefits.

Question 21

What do organisms compete for?

Answer 21

Mates, food, shelter from predators or to protect young,, nesting.

Question 22

Provide some examples of defence mechanisms used in competition.

Answer 22

Teeth, claws, stingers, camouflage, mimicry, poisons and venom

Question 23

What are the three types of symbiotic relationships?

Answer 23

Mutualism, commensalism, parasitism

Question 24

What is mutualism?

Answer 24

Interspecific interaction where both species benefit.

Question 25

Describe how coral and algae operate in a mutualistic relationship.

Answer 25

The algae live, reproduce and photosynthesise in the host coral, feeding off of its waste products. The coral uses the oxygen and food produced by the algae to grow and reproduce.

Question 26

Describe how sea anemone and clown fish operate in a mutualistic relationship.

Answer 26

The anemone fish has a mucus coating which prevents it from being stung. The fish is protected from predators by hiding in the anemone’s tentacles. It feeds on the anemone’s food scraps. The anemone benefits as it is cleaned, and the fish lures prey to its tentacles.

Question 27

What is commensalism?

Answer 27

One species benefits, while the other is unaffected.

Question 28

How are epiphytes an example of commensalism?

Answer 28

Epiphytes such as mosses and ferns live on the branches and trunks of tall trees to get better access to rain and sunlight. The host tree is unaffected.

Question 29

How are barnacles an example of commensalism?

Answer 29

Some barnacles live on the surface of whales and turtles. They do not affect their host, but they are transported to diverse areas rich in food (plankton)

Question 30

What is parasitism?

Answer 30

Relationship where one species benefits, and the other is harmed. The parasite obtains shelter from the host and feeds on its tissues and fluids.

Question 31

What are ectoparasites?

Answer 31

Endoparasites live on the surface of the host, where they suck body fluids, cause irritation, and may act as vectors for pathogens.

Question 32

What are some example of ectoparasites?

Answer 32

ticks, mites, lice, bed bugs, and fleas

Question 33

What are endoparasites?

Answer 33

Parasites that live inside the host, in organs or blood vessels. They have specialised mouthparts and lack of a digestive tract, enable them to spend their life inside the intestines of their vertebrate hosts.

Question 34

Provide some examples of endoparasites.

Answer 34

Tapeworm, heart worm

Question 35

Provide an example of a parasitic plant.

Answer 35

Mistletoe attaches to and penetrate the branches of trees to absorb water and nutrients from the host.

Question 36

What is amensalism?

Answer 36

Describes the situation where the presence of one species has a harmful effect on the other, but is not itself affected by the association.

Question 37

Provide an example of amensalism?

Answer 37

Grazing mammals trample and destroy vegetation around waterholes, creating bare zones. The mammals are unaffected by the loss as they go there primarily to drink and not to feed.