Chapter 19

Question 1

Define environment

Answer 1

The surroundings or conditions in which an organism operates

Question 2

Define biosphere

Answer 2

The regions of the Earth that are occupied by living organisms

Question 3

Define ecosystem

Answer 3

A geographic area of organisms (biotic factors) and their environment (abiotic factors) functioning together as a unit

Question 4

What is a niche?

Answer 4

The match of a species to a specific environmental condition

Question 5

What are the 4 factors that determine population size?

Answer 5

Birth rate, death rate, immigration, and emigration

Question 6

Describe the abiotic factors that affect population size

Answer 6

Rainfall, temperature, pH, sunlight

Question 7

What is intraspecific competition?

Answer 7

Competition between organisms of the same species

Question 8

Summarise the factors that different species compete for.

Answer 8

Biotic factors include food, mates, and territory. Abiotic factors include water, sunlight, space, and nutrients.

Question 9

What is interspecific competition?

Answer 9

Competition between different species due to overlapping niches

Question 10

How does interspecific competition influence population size?

Answer 10

Limits population growth as limited resources progressively decrease in availability. Can also lead to niche differentiation where species evolve to adapt their niches in order to reduce competition which will increase population size.

Question 11

Define population

Answer 11

The total number of organisms of one species in a given area at a given time.

Question 12

Define community

Answer 12

All the populations of different species living and interacting in the same area at the same time

Question 13

Define habitat

Answer 13

The natural home of an organism and the physical area in which it lives

Question 14

What is predation?

Answer 14

The process of one organism (the predator) killing and eating another organism (the prey)

Question 15

How does the predator-prey relationship affect the population size of predator and prey?

Answer 15

Predators eat prey therefore reducing prey population. There is then increased competition between predators for the remaining prey leading to a reduction in predator population. This leads to prey population increasing as there are fewer predators so they are more likely to survive and reproduce. The increased prey population then leads to the predator population rising due to more food availability. The populations of both organisms will constantly fluctuate.

Question 16

What are the factors to be considered when using a quadrat?

Answer 16

Quadrat size, unbiased placement, number of quadrats, species mobility

Question 17

How can a transect be used to obtain quantitative data about changes in communities along a line?

Answer 17

Using a transect allows differences in species diversity/abundance along a line to be measured as well as differences in availability of abiotic factors.

Question 18

How can the abundance of different species be measured?

Answer 18

Quadrat sampling by placing quadrats at random areas and counting the number of species present in each to obtain an estimate for the total number of species in the area.

Question 19

Explain the mark release recapture method.

Answer 19

Mark a recorded number of individuals in a population (Sample 1) and release. Take a random sample of a recorded number of individuals (Sample 2) from the population again and count how many are marked (Sample 2 marked individuals). Multiply Sample 1 by Sample 2 and divide this number by the number of marked individuals in sample 2.

Question 20

Describe the stages of succession.

Answer 20

Pioneer species colonise barren land and help to stabilise the environment and create soil. As soil develops conditions become less harsh and grasses and shrubs begin to grow. Plants and small trees may follow increasing biodiversity. Climax community is reached where the ecosystem is now stable. Can be mature forests and a variety of species which are well adapted to the local environment.

Question 21

What is succession?

Answer 21

The process of change and development in the species composition of an ecological community over time.

Question 22

What is the difference between primary and secondary succession?

Answer 22

Primary is a slow process where species composition changes in a previously uninhabited area. Secondary succession is a rapid process where species composition changes due to the land being altered.

Question 23

What is a pioneer species and what are its characteristics?

Answer 23

The first organism to colonise a barren area of land. Able to withstand extreme conditions, rapid growth rate, soil formation, minimal resource requirements.

Question 24

What is a climax community and what are the characteristics of one?

Answer 24

A stable and mature ecological community that has reached the final stage of succession. Stable, high biodiversity, less hostile environment.

Question 25

How can managing succession help to conserve habitats?

Answer 25

Species are often removed from an area when a climax community is reached as their habitats are lost due to succession. By stopping succession from reaching a later stage we can preserve these habitats.

Question 26

What is meant by conservation?

Answer 26

The management of the Earth’s natural resources by humans in order to preserve them for the future.

Question 27

Describe the competitive exclusion principle.

Answer 27

Two species competing for the same resources cannot coexist indefinitely whilst occupying the same niche. This is because one species will typically have an advantage over the other when facing resource limitation and over time will outcompete the other to extinction or to occupy a different niche.