Populations and Ecosystems

Question 1

What is the biosphere?

Answer 1

The life supporting layer of land, air and water that surrounds the Earth.

Question 2

What is an Ecosystem

Answer 2

A specific area made of interacting biotic and abiotic features. There are two main processes: the flow of energy through the system and the cycling of elements within the system.

Question 3

What is a population?

Answer 3

A group of interbreeding organisms of one species in a habitat.

Question 4

What is a community?

Answer 4

All the populations of different organisms living and interacting in a particular place at the same time.

Question 5

What is a habitat?

Answer 5

Where a community of organisms live.

Question 6

What is an ecological niche?

Answer 6

How an organism fits into the environment.

Question 7

Investigating populations things

Answer 7

Quadrats
Random Sampling
Systematic sampling
Measuring Abundance
Mark-release-recapture techniques

Question 8

Quadrats: what do we need to consider when using them?

Answer 8

Size of quadrat depends on size of subject organism
Number of sample quadrats to record within the area
Position of each quadrat within the area

Question 9

Random sampling

Answer 9

Avoids bias
Random numer generator to get coordinates
Count frequency of species or organisms within the quadrat

Question 10

Systematic sampling

Answer 10

Use transects
Used to investigate transitions
e.g: to measure the abundance of grass from the trunk of the oak tree on the field to the middle of the field.

Question 11

Measuring abundance: what does it measure?

Answer 11

Frequency

Percentage cover

Question 12

Mark-release-recapture

Answer 12

Estimated population size =

(total individuals in 1st sample x total individuals in 2nd sample) / number marked individuals recaptured

Question 13

Mark-release-recapture only works under which assumptions?

Answer 13

The proportions marked and unmarked in the 2nd sample is the same as the marked and unmarked in the total population.
Marked individuals spread evenly throughout the population.
Closed system: no immigration or emigration.
No deaths or births
Marking provides no disadvantage (e.g: doesn’t makes individual more conspicuous)
Marks not rubbed off, or lost.

Question 14

Population growth curves have which stages

Answer 14

Slow growth
Rapid growth
Plateau with fluctuations

Question 15

Abiotic factors

Answer 15

Temperature
Light intensity
pH
Water and humidity

Question 16

Biotic factors

Answer 16

Availability of food
Presence of predators
Disease

Question 17

What is infraspecific competition?

Answer 17

Individuals of the same species compete for resources like food, water and breeding sites

Question 18

What is interspecific competition?

Answer 18

Individuals of different species compete for resources like food, light, and water

Question 19

What is a predator?

Answer 19

A predator is an organism that feeds on another organism known as their prey

Question 20

Predator prey relationship

Answer 20

Predators eat their prey –> reducing prey population
Less prey –> more competition between each other
Decrease in predator population as some can’t eat enough
Less predators –> few prey eaten
Increase in prey population –> more to eat for predators
Predator population increases

Question 21

Factors affecting growth and size of human populations

Answer 21

Immigration
Emigration
Birth rate
Death rate

Question 22

Factors affecting birth rate

Answer 22

Economic conditions –>generally LEDCs = high BR
Religious backgrounds –> some religions oppose birth control and encourage larger families
Social pressures –> large families = higher social standing
Birth control –> availability of contraception and abortion
Political factors –> education and tax policies

Question 23

Factors affecting death rate

Answer 23

AGE PROFILE –> ageing = more elderly = more deaths
LIFE EXPECTANCY a birth
Availability of FOOD and a balanced diet
SAFE DRINKING WATER and effective sanitation –> less water-borne diseases e.g: cholera
MEDICAL CARE
NATURAL DISASTER frequency: drought, famine, disease or tectonic or meteorological = high death rate
WAR