3.4.1 Populations

Question 1

What is an abiotic factor?

Answer 1

Non-living factors such as temperature and oxygen availability that affect the distribution of living organisms

Question 2

What is an Ecological Community?

Answer 2

All the living organisms in a defined area

Question 3

What is a Population?

Answer 3

The total number of a single species living in a defined area e.g. Bladder wrack

Question 4

What is a habitat?

Answer 4

The abiotic part of an ecosystem; the place where an organism lives e.g. Rocky shores

Question 5

What is an Ecological Niche?

Answer 5

The role of an organism in a community

Question 6

What is a quadrat?

Answer 6

A square frame used to measure the distribution of organisms along a transect.

Question 7

What is species frequency?

Answer 7

Number of samples found/total number of samples * 100

Question 8

What is percentage cover?

Answer 8

The percentage of each quadrat sample that the organism covers

Question 9

What is a transect

Answer 9

A technique for measuring the influence of an environmental gradient on organisms

Question 10

What is a community?

Answer 10

All the living organisms in a defined area e.g. Rocky Shore community

Question 11

What is an ecosystem?

Answer 11

A reasonably self contained functional unit

Question 12

What is interspecific competition?

Answer 12

Competition for resources between species

Question 13

What is intraspecific competition?

Answer 13

Competition for resources within a species

Question 14

What is a biotic factor?

Answer 14

Living factors like predators and competition that affect the distribution of organisms in the ecosystem

Question 15

How does temperature affect variation in population size?

Answer 15

Every species has optimal temperature, further away from that optimal temperature, the smaller number that can survive. Too high and enzymes denature, too low and enzymes slow down too much

Question 16

How does light affect the variation of population size?

Answer 16

Light intensity affects the rat for photosynthesis. Faster photosynthesis means bigger populations for plants, so more food for animals, so bigger population for animals.

Question 17

How does pH affect variation in population size?

Answer 17

Affects enzyme action. The closer to optimal pH, the bigger the population will be

Question 18

How does water and humidity affect the variation in population size?

Answer 18

Only organisms adapted to dry conditions can survive where water is scarce and the air is dry. Humidity affects transpiration in plants and evaporation of water from the bodies of animals.

Question 19

How does interspecific competition affect the variation in population size?

Answer 19

If two species are competing, the one with the advantage will grow in size, while the other will diminish

Question 20

How does intraspecific competition affect variation in population size?

Answer 20

The higher the availability of resources, the larger the population because as they don’t have to compete

Question 21

What is Random Sampling?

Answer 21

A method of sampling which reduces bias using random coordinates

Question 22

What is Mark release recapture and how can it be used to investigate population size?

Answer 22

A method used in ecology used to estimate population size by capturing, marking releasing, and recapturing. Upon a random recapture the number of marked organisms can be used to calculate a Lincoln index to estimate the overall size

Question 23

What is systematic sampling?

Answer 23

Sampling at regular intervals

Question 24

Ethics of mark release recapture?

Answer 24

Can distress or harm the animal.

Question 25

What can be used to analyse data to investigate populations?

Answer 25

Statistics and Kite a Diagrams

Question 26

Describe how you could use the mark-release-recapture method to estimate the number of a species

Answer 26

Capture, mark and release
Method that does not harm the animal
Leave sufficient time for the animals to then randomly distribute
Population = number in the first sample x number in second sample divided by number of marked lizards recaptured

Question 27

What is the formula for birth rate?

Answer 27

Number of births in a year x (1000/total population that year)

Question 28

What is the formula for death rate?

Answer 28

Number of deaths in a year x (1000/total population that year)

Question 29

What is the formula for percent growth?

Answer 29

(population increase during year/population at the start of the year) x100

Question 30

What changes occur in the birth and death during demographic transition?

Answer 30

Birth and Death rate both fall, then level out/stabilise

Question 31

What changes occur in population size over the course of demographic transition?

Answer 31

Population increases then levels off/stabilises

Question 32

Suggest reasons why men’s life expectancy is lower than women’s

Answer 32

Stress, Obesity, War, Less likely to visit the doctor, Sex-linked diseases

Question 33

What do different age pyramid shapes indicate?

Answer 33

• Wide base = high birth rate
• Quick narrowing = short life expectancy
• Wide top = Low death rate/long life expectancy

Question 34

How can you read life expectancy off of a survivor curve?

Answer 34

Reading off the age that 50% of people survive.