Populations

Question 1

Give a definition for a species

Answer 1

A group of organisms that can interbreed and produce fertile offspring

Question 2

What is a population?

Answer 2

All the organisms of a particular species living in a habitat at a particular time

Question 3

Define community

Answer 3

All living organisms of all species found in a habitat at a particular time

Question 4

Define ecosystem

Answer 4

All the living organisms found in a self contained area and their interactions with the non-living abiotic factors.

Question 5

What is an abiotic factors and give two examples?

Answer 5

None living feature of an ecosystem
Light intensity, temperature, pH, wind speed, water availability, mineral availability, wavelength of light, oxygen concentration

Question 6

What is a biotic factor and give two examples?

Answer 6

Living features of an ecosystem

Predators, food availability, pathogens

Question 7

What is a habitat?

Answer 7

The place where an organism lives within an ecosystem

Question 8

What is meant by the term niche

Answer 8

The role of a species in a habitat consisting of both its biotic interactions eg what it eats and abiotic interactions eg time of day it is active
Two species can not occupy the same niche

Question 9

What is meant by carrying capacity

Answer 9

The maximum size of population an ecosystem can support

Question 10

What is meant by intraspecific competition?

Answer 10

Competition for resources between organisms of the SAME species

Question 11

What is meant by interspecific competition?

Answer 11

Compensation for resources between organisms of DIFFERENT species.

Question 12

Name three resources organisms might compete for.

Answer 12

Food, water, space/territory/shelter, minerals, light, mates (intraspecific only)

Question 13

Describe how you would use a quadrat to estimate the size if a non-motile species

Answer 13

Two tape measures placed at 90 degrees to each other to form a grid
Random number generator used to identify coordinates
Quadrat placed at coordinates
Count the number of species
Repeat large number of times to gain a representative sample
Calculate mean number of the species
Carry out appropriate calculations to estimate the population in the whole area under surveillance

Question 14

Describe how to carry out mark release recapture for estimating the size of a motile population

Answer 14

Capture a sample of the population and count
Mark the organisms
Release back into the habitat
After a period of time capture another sample of the population and count the number of marked and unmarked organisms
Use a formula to estimate the population size

Question 15

What is the equation for estimating the population size using mark-release-recapture?

Answer 15

Population =
no. of organisms in first sample x total no. of organisms in second sample
——————————————————————————–
No. of marked individual recaptured

Question 16

What assumptions does mark-release-recapture method make?

Answer 16

Marked individuals are evenly distributed in population
No migration or immigration
Large sample size
Few deaths or births
Method of marking does not affect survival
Mark does not come off.

Question 17

What is succession?

Answer 17

The changes in the community that occurs over time in an area

Question 18

Summarise the process of primary succession

Answer 18

Pioneer species can survive hostile conditions and colonise the area
Change abiotic factors in the environment eg decomposition increases minerals and soil depth
Allows more complex organisms to survive

Question 19

What is a climax community and how is it reached?

Answer 19

Final stage of succession.
Ecosystem is balanced and stable
Soil is rich enough to support large trees
Environment is no longer changing

Question 20

What is meant by the term conservation?

Answer 20

Protection and management of species and habitats to maintain biodiversity

Question 21

Why is a log scale used on a graph recording the population of bacterial cells?

Answer 21

LARGE RANGE in numbers.

Allows patterns and trends to be seen

Question 22

Describe how you would determine the mean percentage cover of grass on a sand dune.

Answer 22

Two tape measures placed at 90 degrees to each other
Random number generator used to identify coordinates
Quadrat placed at interception of coordinates
Estimate the percentage cover of grass
Repeat a large number of times to gain a representative sample
Divide total percentage in all samples by the number of quadrats taken

Question 23

What is a pioneer species and how is it adapted?

Answer 23

First organisms to colonise a hostile environment.
Can survive with few minerals, little water, lack of soil.
Vast amount of wind dispersed seed/spores that can reach isolated areas.
Rapidly germination
Ability to photosyntheise

Question 24

Give an example of a pioneer species and state how it is adapted

Answer 24

Lichen

Consists of algae that photosynthesise to produce organic material and fungus which reduces water loss.
Reproduce by spores

Question 25

Which species follows after lichens in succession?

Answer 25

Mosses

Question 26

How do animal populations change during succession?

Answer 26

Also undergo successional change

Determined by the different types of plants available for food and habitats.

Question 27

What are the common changes that occur during succession?

Answer 27

Abiotic environment becomes less hostile
Greater number of and variety of habitats and niches
Increased biodiversity
Increased VARIETY of food sources
More complex food webs
Increased biomass

Question 28

What is the difference between primary and secondary succession?

Answer 28

Primary succession begins on bare rock, with no soil. Takes longer to reach the climax community
Secondary succession starts on land that already has soil. Climax community achieved quicker.

Question 29

When would use a transect?

Answer 29

Looking for a change in the organisms present over a certain distance.
Use when there is a transition in conditions
eg up a hill, a tidal seashore, distance from a source of pollution

Question 30

How would you carry out a transect on a sand dune?

Answer 30

Place a tape measure from the sea edge of the sand dune away from the sea.
Place a quadrat at REGULAR intervals eg every 2 metres
Record the species present and relative amounts.
Repeat transect several time

Question 31

Succession is …

Answer 31

How an ecosystem changes with time

Question 32

Give examples of human activities that prevent succession.

Answer 32

Mowing lawn, grazing animals, managed fires