Biotic factors

Question 1

deterring predators (4)

Answer 1

some animals and plants have special features that deter predators

• some animals advertise that they are poisonous with very bright colours (e.g. tree frogs)
• some animals use colours to make them look more frightening (e.g. the ‘eyes’ on a butterfly)
• some plants have big thorns
• other plants are poisonous

Question 2

Why is there competition between organisms for materials?

Answer 2

organisms need a supply of materials from their surroundings or from other living organisms to survive and reproduce

this means that there is competition between organisms for materials in limited supply

Question 3

Give two examples of competition between plants

Answer 3

competition for light and space above ground

competition for water and nutrients below

Question 4

Give 3 examples of competition between animals

Answer 4

food

mates for reproduction
(so they can pass on their genes to their offspring, this often results in fights, so only the strongest pass on their genes)

territory
(space for feeding, reproducing, and raising young, and it contains all the resources and conditions needed to survive, including a/biotic factors)

Question 5

In spring, a male robin will sing loudly.

Explain the role of singing in robins in terms of competition. [2]

Answer 5

a male robin competes with other robins for mates and for territory

singing loudly warns other males to keep out of the robins territory, and attracts females who choose to mate with him

Question 6

The ground underneath the trees in the wood is mostly bare.

Explain why very few plants can grow here. [2]

Answer 6

there is very little light underneath the trees in a wood, plants are unable to compete with the trees for the sunlight

Question 7

A farmer plants the seeds of his crop plants so that they are well separated from each other.
Explain why. [2]

Answer 7

so that the plants do not compete for an environmental factor such as light/water/nutrients

Question 8

Milk snakes are non poisonous snakes. Coral snakes are highly poisonous. Milk snakes that live in the samea area as coral snakes have a bold red and black pattern that is similar to that of the coral snakes. Suggest the advantage to the milk snake of this patterning. [2]

Answer 8

predators of milk snakes may confuse them with the poisonous coral snakes and will avoid them because they know that coral snakes are poisonous

Question 9

biotic factors (4)

Answer 9

availability of food
(all animals need food to live, so more food means more animals)

new predators
(new predators in an ecosystem can have a devastating effect, reducing the amount of prey for other predators)

new pathogens
(organisms haven’t evolved resistance to new pathogens, so are more vulnerable to them)

competition
(species can out-compete others for resources, lowering their numbers)

Question 10

intraspecific competition

Answer 10

the competition between organisms within the same species

Question 11

interspecific competition

Answer 11

the competition between organisms within different species

Question 12

stable community

Answer 12

where the size of the populations of all species remains relatively constant over time, and are in a healthy balance with the environment