3.7.3 Populations and Ecosystems

Question 1

Why is it important to measure species diversity?

Answer 1

to compare different habitats or study how a habitat has changed over time

Question 2

Answer 2

Question 3

Define niche

Answer 3

The role of a species in it’s environment

Question 4

Define community

Answer 4

All of the organisms of different species that live in the same habitat and interact with each other

Question 5

Define population

Answer 5

All the organisms of one species in a habitat

Question 6

Define mutualism

Answer 6

A relationship between two organisms where both benefit

Question 7

Define ‘population size’

Answer 7

The number of individuals of one species in a particular area

Question 8

Define ecosystem

Answer 8

All the organisms living in a particular area and all the non living (abiotic) factors

Question 9

Define habitat

Answer 9

The place where an organism lives

Question 10

Define species distribution

Answer 10

Where a species is within a particular area

Question 11

Define abundance

Answer 11

The number of individuals of one species in a particular area

Question 12

Define biotic factors

Answer 12

The living features of the ecosystem (e.g. predators, prey, microorganisms)

Question 13

Define abiotic factors

Answer 13

The non living features of the ecosystem

Question 14

Define carrying capacity

Answer 14

The maximum stable population size of a species

Question 15

What happens as a population of organisms approaches carrying capacity (k strategist)

Answer 15

Density dependent factors limit the rate of population growth (eg availability of food). This is sometimes referred to as environmental resistance

Question 16

How can some organism have a polulation above carrying capacity

Answer 16

They reproduce very quickly (often small organisms - R strategists) and a population boom will be followed by a bust (dramatic decrease).

Question 17

what formula determines the size of a bacterial population growing exponentially

Answer 17

Population = Starter population x 2^n (where n = number of generations)

Question 18

why do we often use logarithmic graphs when plotting bacterial populations

Answer 18

When the populations have a very large range (ie you have to plot very small numbers and very large numbers)

Question 19

What is a producer (or an autotroph)?

Answer 19

Organisms that produce their own food (usually through photosynthesis)

Question 20

Which factors determine the numbers and distribution of organisms in a habitat ?

Answer 20

Biotic and Abiotic factors

Question 21

What is primary succession?

Answer 21

Occurs on land that has been newly formed or exposed

Question 22

What is secondary succession?

Answer 22

Occurs on land that has been cleared of all plants, but where the soil remains

Question 23

What is a climax community?

Answer 23

A stable community usually dominated by trees that remains unchanged unless conditions in the habitat change

Question 24

What is a pioneer species?

Answer 24

The first species to colonise an area, tends to be very specialised

Question 25

How does primary succession start?

Answer 25

When species colonise a new land surface, seeds and spores are blown in by the wind and begin to grow

Question 26

Describe the abiotic conditions at the start of primary succession

Answer 26

Hostile, there is no soil to retain water

Question 27

How can pioneer species grow in primary succession?

Answer 27

They are specially adapted to cope with the harsh conditions (extremes of temp, lack of soil, water and nutrients)

Question 28

How do pioneer species change the abiotic conditions ?

Answer 28

They die and microorganisms decompose the dead organic material forming basic soil. So the conditions are less hostile

Question 29

When the conditions are less hostile what happens (primary succession) ?

Answer 29

the basic soil retains water so new organisms with different adaptations move in and grow. these then die and decompose adding more organic material, making the soil deeper and richer in minerals

Question 30

Define dominant species

Answer 30

Outcompete the plants and animals that are already there as they are better adapted. They are the most abundant species.

Question 31

What is interspecific competition ?

Answer 31

when organisms of different species compete with each other for the same resources

Question 32

What is intraspecific competition ?

Answer 32

When organisms of the same species compete with each other for the same resources

Question 33

what is the competitive exclusion principle and can you draw a graph of paramecium populations to illustrate

Answer 33

If 2 organisms with a similar niche are grown in a habitat or culture, only one will survive.

Question 34

What is the carrying capacity of a population?

Answer 34

The maximum stable population size of a species

Question 35

How are the population sizes of predators and prey interlinked ?

Answer 35

as the population of one changes, it causes the other population to change

Question 36

What happens when the prey population increases?

Answer 36

There is more food for predators so the predator population grows

Question 37

What happens when the predator population grows?

Answer 37

More prey is eaten so the prey population decreases

Question 38

What do grazing, predation and parasitism have in common ?

Answer 38

They are relationships between two organisms where one benefits at the others expense

Question 39

what is conservation

Answer 39

the management of the earths natural resources by hyuman in such a way that maximum use of them can be made in the future

Question 40

What are some different types of reasons to conserve ecosystems and biodiversity

Answer 40

Personal reasons, ethical reasons (it is the right things to do), economic reasons (the ecosytem provides ecosytem services such as pollination and clean air), cultulral and aesthetic reasons

Question 41

why might conservationists sometimes prevent succession

Answer 41

In some cases, transitional communities may have higher biodiversity (but lower biomass) than climax communities. This may be true in places like moorland where succession is prevented by either grazing or periodic burning

Question 42

What is deflected succession

Answer 42

Where some activity prevents succession to a climax community. A plagioclimax community is reached instead (eg moorland)