19 Populations in ecosystems

Question 1

Ecology

Answer 1

The study of the inter-relationships between organisms and their environment.

Question 2

What is an ecosystem made up of?

Answer 2

All the interacting biotic and abiotic features in an area.

Question 3

What are the two main processes in an ecosystem?

Answer 3

The flow of energy through the system and cycling of elements within a system.

Question 4

Population

Answer 4

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

Question 5

Community

Answer 5

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

Question 6

Habitat

Answer 6

A place where a community of organisms live. (Within one ecosystem, there are many habitats)

Question 7

Microhabitats

Answer 7

Smaller units within a habitat

Question 8

Niche

Answer 8

Describes how an organism fits into the environment.

Question 9

What could never happen between two species?

Answer 9

Occupying exactly the same niche.

Question 10

What would happen at the start of the population growth curve?

Answer 10

Slow growth - because small number of individuals reproduce slowly to build up numbers.

Question 11

What would happen at the middle of the population growth curve?

Answer 11

Ever increasing number of individuals continue to reproduce (exponential growth)

Question 12

What would happen at the end of the population growth curve?

Answer 12

Stable state - only cycling fluctuations, due to food supply or predator numbers.

Question 13

Carrying capacity

Answer 13

The certain size that each population can be sustained over a long period of time.

Question 14

Limiting factors

Answer 14

Determines the carrying capacity of any population.

Question 15

E.g. of abiotic factors

Answer 15

Light, water, pH and temperature

Question 16

E.g. of biotic factors

Answer 16

activities of living organisms - competition and predation

Question 17

How does each abiotic factors affect population size?

Answer 17

Temperature: Optimum temperature for different species. Enzymes activity etc.
Light: Photosynthesis, affects food chain.
pH: action of enzymes.
Water & humidity: essential to growth and living. Humidity affects rate of transpiration.

Question 18

Reasons causing human population explosion.

Answer 18

1. Development of agriculture
2. Development of manufacturing and trade created by the industrial revolution.
3. Medicine, increases life expectancy.

Question 18

Factors affecting the growth and size of human populations

Answer 18

Basic factors: birth rate and growth rate
Individual populations: immigration and emigration

Question 19

Equation for population growth.

Answer 19

(births + immigration) - (deaths + emigration)

Question 20

Equation for %population growth rate (in a given period)

Answer 20

Population change during the period/ population at the start of the period x100

Question 21

Factors affecting birth rates

Answer 21

• Economic conditions
• Cultural and religious backgrounds
• Social pressures and conditions
• Birth control
• Political factors

Question 22

Equation for Birth rate

Answer 22

number of births per year/ total population in the same year x100

Question 23

Factors affecting death rates

Answer 23

• age profile (general age of the population)
• life expectancy at birth
• food supply
• safe drinking water and effective sanitation
• medicinal care
• natural disasters
• war

Question 24

Demographic transition

Answer 24

Happens in well developed countries, cause a long life expectancy and low birth rate