Populations and Ecosystems

Question 1

What is an ‘ecosystem’?

Answer 1

all of the living and non-living components of a particular area

Question 2

What is meant by the term ‘abiotic factors’?

Answer 2

an ecological factor that makes up part of the non-biological environment

Question 3

What is meant by the term ‘biotic factors’?

Answer 3

an ecological factor that makes up part of the living environment

Question 4

What is meant by the term ‘population’?

Answer 4

a group of individuals of the same species that occupy the same habitat at the same time

Question 5

What is meant by the term ‘habitat’?

Answer 5

the place where an organism normally lives and which is characterised by the physical conditions and the types of organism present

Question 6

What is meant by the term ‘species’?

Answer 6

a group of similar organisms that can breed to produce fertile offspring

Question 7

What is meant by the term ‘community’?

Answer 7

all of the living organisms present in an ecosystem at a given time

Question 8

What is meant by the term ‘niche’?

Answer 8

describes how an organism fits into its environment. (includes: what the species is like; how it responds; how it behaves; where it occurs)
NO 2 SPECIES CAN OCCUPY THE SAME

Question 9

Give 4 things that can impact population size

Answer 9

• intraspecific competition
• interspecific competition
• predation
• abiotic factors (e.g, water, pH, temp.)

Question 10

Give 3 things that can be competed for between different species

Answer 10

• water
• food (nutrients if talking about plants)
• space/territory

Question 11

Give 3 things that can be competed for between organisms of the same species

Answer 11

• mates/breeding sites
• food
• space
• water

Question 12

Why might a correlation not show the casual effect (on a graph showing time and population size)?

Answer 12

correlation ≠ causal effect
it could be caused by other biotic factors, such as interspecific competition.
One species could have outcompeted the other for (a specific resource)

Question 13

Why does interspecific competition take longer to influence population size?

Answer 13

• lots more factors involved
• death and birth rates

Question 14

How might an increase in intraspecific competition drive natural selection?

Answer 14

if caused by change in environment, may lead to one species having a selected advantage for a particular species

Question 15

In relation to competition, how would less resources impact population size?

Answer 15

less resources (food, space, water)
means more competition
would reduce population size if the species which is outcompeted

Question 16

How is temperature a limiting factor of the carrying capacity of a population?

Answer 16

• enzymes in plants, bacteria and reptiles will denature (no thermoregulation)
• in mammals; more energy is needed to maintain body temperature so less energy is available for growth and reproduction

Question 17

What biotic factors could limit carrying capacity?

Answer 17

• diseases
• predation
• intra and interspecific competition

Question 18

What is meant by the term ‘carrying capacity’?

Answer 18

the maximum stable population size of a species that an ecosystem can support

Question 19

Why is the population size of predator and prey limited in stable communities?

Answer 19

as the numbers of prey are increasing and decreasing in cycles

Question 20

Why might nutrients leaking into lakes cause fish populations to decrease?

Answer 20

• algal bloom blocks sunlight
• reduced photosynthesis causes plants to die
• saprobionts respire aerobically
• less oxygen for fish to respire

Question 21

How might digesting other organisms allow plants to grow in places with little nutrients available?

Answer 21

• nutrients such as proteins can be broken down
• provides amino acids that can be used to make proteins in the plant

Question 22

disease X is caused by an insect. How would introducing infertile insects reduce the transmission of disease X?

Answer 22

• intraspecific competition for mates, food and space
• insects do not reproduce
• fewer insects

Question 23

disease X is caused by an insect. Why might introducing infertile insects NOT reduce disease X?

Answer 23

• impacts courtship behaviour
• affects survival