Populations and Ecosystems

Question 1

ecology definition

Answer 1

the study of the inter-relationships between organisms and their environment which includes both living (biotic) and non-living (abiotic) factors

Question 2

environment definition

Answer 2

the biotic and abiotic factors in a habitat affecting an organism and ultimately affecting its survival

Question 3

what are factors that must be considered in an ecosystem?

Answer 3

1 how energy flows through the system (biomass)
2 how important elements are cycled through the system

Question 4

community definition

Answer 4

the populations of the different species that live and interact in the same place at the same time

Question 5

population definition

Answer 5

a group of interbreeding organisms of the same species living together in a habitat at the same time

Question 6

what is carrying capacity?

Answer 6

the maximum number of organisms of a particular species that can be supported by a habitat

Question 7

why is there a carrying capacity in a articular ecosystem?

Answer 7

the effect of abiotic factors
interactions between other organisms eg. predation, competition

Question 8

habitat definiton

Answer 8

the place where an organism lives and is characterised by the physical conditions and other types of organisms present

Question 9

what can single habitats be made up of?

Answer 9

several different microhabitats

Question 10

microhabitat definition

Answer 10

smaller subunits within habitats that have their own microclimate

Question 11

ecological niche definition

Answer 11

the niche of a species is its role in the community. it describes all the conditions and resources required for an organism to survive and reproduce to maintain a viable population

Question 12

what is the competitive exclusion principle?

Answer 12

no two species can occupy the same niche in the same habitat at the same time

Question 13

difference between niche and habitat

Answer 13

a species habitat will almost always overlap with many other species but the way each species uses the habitat will differ to varying degrees

Question 14

a typical population growth curve with key features

Answer 14

• slow growth
• rapid growth
• carrying capacity
• stable state, no growth
• small fluctuations due to changes in factors such as food supply

Question 15

explain the slow phase (pop curve)

Answer 15

a period of slow growth as the initially small number of individuals begin to reproduce and slowly build up their numbers

Question 16

explain the rapid growth (pop curve)

Answer 16

the ever increasing numbers of individuals continue to reproduce. the population size doubles with each interval of time as seen by the steep gradient of the graph

Question 17

explain the stable/stationary phase (pop curve)

Answer 17

population growth declines until its size remains more of less stable. the decline is due to limiting factors such as availability of food or predation. the graph levels out with only cyclic fluctuations in population size due to variations in factors e.g. predator population size or food supply

Question 18

what are biotic factors?

Answer 18

any living factors, e.g. disease, predation, competition for food

Question 19

what are abiotic factors?

Answer 19

any non-living factors, e.g. light, rainfall, pH, temperature

Question 20

how does temperature affect the population?

Answer 20

each species has an optimum temperature, further from the optimum, less of the species can be supported. as temp falls below the optimum, enzyme activity falls, so metabolic rate is reduced. above optimum, enzymes are denatured.

Question 21

how does light affect population?

Answer 21

as light intensity increases, so does the rate of photosynthesis. greater rate of photosynthesis, faster growth and more spores/seeds produced. animals feed on these plants so their pop increases.

Question 22

how does pH affect population?

Answer 22

affects the action of enzymes. appropriate pH = larger pop. very different pH = smaller/non-exsistent pop

Question 23

how does water and humidity affect population?

Answer 23

where water is scarce, pops consist of well-adapted species. humidity affects transpiration rates in plants and the evaporation of water from the bodies of animals. in dry conditions, species adapted for this will have a larger population than those with no adaptions.

Question 24

When does competition occur?

Answer 24

When two or more individuals share any resource that is insufficient to satisfy all their requirements fully

Question 25

What is intraspecific predation?

Answer 25

Between the same species

Question 26

Why might intraspecific predation occur?

Answer 26

• for scarce resources
• availability of these resources will determine the size of the population
• larger availability of resources = larger population

Question 27

What is interspecific predation?

Answer 27

Between different species

Question 28

Why does interspecific predation occur?

Answer 28

• when populations of two species occupy the same niche, one will have a competitive advantage over the other

Question 29

Why does interspecific predation occur?

Answer 29

• when populations of two species occupy the same niche, one will have a competitive advantage over the other