3.4.1 - Populations

Question 1

Abiotic factors definition

Answer 1

A non- living factor within the ecosystem

E.G. The air/ temperature

Question 2

Biotic factor definition

Answer 2

Living elements within an ecosystem

E.G. Animals/ plants

Question 3

Population definition

Answer 3

Groups of individuals that belong to the same species

Question 4

Species definition

Answer 4

A group of closely related organisms which are similar and capable of producing fertile offspring

Question 5

Community definition

Answer 5

An interacting group of various species in a common location

Question 6

Habitat definition

Answer 6

The place where a community of organisms lives

Question 7

Niche definition

Answer 7

The way in which an organism fits into an ecosystem. A niche is the evolutionary result of a species physiological and behavioural adaptations to its surroundings

Question 8

Adaptation definition

Answer 8

Changes in behaviour, physiology and structure of an organism to become more suited to an environment. Achieved through the process of natural selection

Question 9

Ecosystems definition

Answer 9

Community of living organisms in conjunction with their non-living components of their environment

Question 10

What factors to consider when using a quadrat?

Answer 10

1. The size of the quadrat in respects to the size of the species and the distribution
2. The number of samples quadrat a to record, if use more, results are more reliable but not take up too much time
3. The position of each quadrat (use random number generator calculator)

Question 11

Why is random sampling used?

Answer 11

To avoid any bias in collecting data, ensuring the data is valid

Question 12

How is sampling made random?

Answer 12

1. Lay out 2 long tapes at right angles along both sides of area
2. Obtain coordinates using random numbers generated from a calculator
3. Place a quadrat at the intersection, collect data

Question 13

Mark release recapture method

Answer 13

1. A known number of organisms are collected, marked in some way and released back into the community
2. After some time, a number of individuals are collected randomly

Question 14

Estimates population size formula

Answer 14

= (No. of individuals in the 1st sample X the second sample) ———————————————————————————
No. of marked individuals recaptured

Question 15

Assumptions of the mark-release-recapture method?

Answer 15

Few, if any, deaths of births within the population
Marking doesn’t hinder the chance of survival of the animal
Marking doesn’t rub off

Question 16

Example of a systematic sample?

Answer 16

A line transect, collecting data at set intervals

Question 17

First stage of DTM?

Answer 17

Small stable population, high birth and death rates

Question 18

Second stage of the DTM?

Answer 18

Early expansion of population, high birth rates and decreasing death rates

Question 19

Third stage of DTM?

Answer 19

Late expansion of the population, decreasing birth rates and low death rates

Question 20

Predator definition

Answer 20

Organism that feeds on other organisms

Question 21

Predator prey cycle description

Answer 21

Predators eat prey, reducing prey population
More competition between predators (less prey available), reducing predator population
Fewer predators, fewer prey eaten, increase prey population
More prey to eat, increase predator population

Question 22

Why predator prey cycle isn’t realistic?

Answer 22

Organisms eat a wider variety of food, so when prey population reduces, organisms eat other prey
Other factors affect population sizes (disease, environment…)

Question 23

Example of predator prey cycle?

Answer 23

Lynx and hare

Question 24

Population growth equation?

Answer 24

(Births + immigration) - (deaths + emigration)
Or population change during period
——————————–
Population at start of period

Question 25

Factors effecting birth rate?

Answer 25

Economic conditions (low GDP per capita)
Cultural background
Social pressures (of having large family)
Availability of birth control
Political factors (China policy)

Question 26

Birth rate definition

Answer 26

Number of babies born per 1000 people per year

Question 27

Factors affecting death rate?

Answer 27

Age profile
Life expectancy
Food supply
Safe drinking water
Medical care
Natural disasters
War

Question 28

Death rate definition?

Answer 28

Number of deaths per 1000 people per year

Question 29

Birth rate equation

Answer 29

No. of births per year
————————— x1000
Total population same year

Question 30

4th stage of the DTM?

Answer 30

Large stable population, low birth and death rates

Question 31

Average life expectancy=?

Answer 31

Age which 50% of individuals in population are still alive

Question 32

Why does competition occur?

Answer 32

When there are more individuals sharing resources that aren’t sufficient enough to fulfil everyone’s requirements

Question 33

Intraspecific completion definition?

Answer 33

Competition between members of the same species

Question 34

Interspecific competition definition?

Answer 34

Competition between members of different species

Question 35

Why can’t prove changes to population are due to competition?

Answer 35

Many other factors affect population size (disease, war, hygiene…)
Correlation doesn’t mean a clear causal link
A time lag may exist, so the population change may be due to competition years before
Data on populations is hard to obtain and not always reliable

Question 36

Competitive exclusion principle?

Answer 36

Populations of 2 species will occupy same niche and compete
One will have a competitive advantage
This population will gradually increase in size
The other population will diminish, until species is removed