19.1 - 19.7 Populations in ecosystems

Question 1

Define ecosystem

Answer 1

Dynamic systems made up of a community and all non-living factors of its environment

Question 2

Define population

Answer 2

A group of individuals of one species that occupy the same habitat at the same time

Question 3

Define community

Answer 3

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

Question 4

Define habitat

Answer 4

The place where an organism normally lives. Characterised by the physical conditions and other types of organism present.

Question 5

Define ecological niche

Answer 5

How an organism is adapted to survive biotic and abiotic conditions

Question 6

Define intraspecific competition

Answer 6

Individuals of the same species compete with one another for resources

Question 7

Define interspecific competition

Answer 7

Individuals of different species compete for resources

Question 8

Define predation

Answer 8

When one organism is consumed by another

Question 9

Describe the effect of the predator-prey relationship on population size

Answer 9

• Predators eat prey, reducing the population of prey
• With fewer prey, the predators are now in greater competition with each other
• Predator population is reduced due to lack of food
• Fewer predators so fewer prey are eaten
• Prey population increases
• More prey available as food so predator population increases

Question 10

Describe how to carry out the mark-release-recapture technique

Answer 10

1. Collect sample of organisms and mark them in a way that is non-toxic and does not increase their chance of being preyed on
2. Release individuals and leave enough time for them to redistribute back into the population
3. Collect new sample
4. Equation

Question 11

Mark-release-recapture equation

Answer 11

estimated population size =

(total no. in 1st sample) x (total no. in 2nd sample) / no. of marked individuals in 2nd sample

Question 12

What assumptions does the mark-release-recapture method make?

Answer 12

1. Proportion of marked to unmarked in 2nd sample is the same as the whole population
2. Marked individuals distribute evenly
3. No immigration or emigration
4. Equal number/no deaths and births

Question 13

Define succession

Answer 13

The change in an ecological community over time. It occurs in a series of stages called seres. Due to change in abiotic factors and/or species present.

Question 14

How might barren land arise?

Answer 14

• A glacier retreating and depositing rock
• Sand being piled into dunes by wind or sea
• Volcanoes erupting and depositing lava
• Mud deposited by rivers

Question 15

What is the name of the first species to colonise barren land?

Answer 15

Pioneer species

Question 16

List the common features of a pioneer species

Answer 16

• Asexual reproduction
• Vast no. of wind dispersed seed or spores
• Rapid germination
• Able to photosynthesise
• Tolerance to extreme conditions
• Ability to fix nitrogen from the atmosphere

Question 17

Describe succession, starting with lichen

Answer 17

• Lichen colonises bare rock as the pioneer species
• Lichen die and decompose to form a thin soil
• Other species such as mosses can now grow
• Larger species that need more water (grasses, small flowering plants) move in as soil deepens
• Shrubs, ferns and small trees begin to grow and out-compete smaller plants
• Finally, soil is deep and rich enough to support large trees. These become dominant species and a climax community forms.

Question 18

What is a climax community?

Answer 18

The final stable community that exists after the process of succession has occured

Question 19

List some common features of a climax community

Answer 19

• Same species present over long time
• Abiotic factors more or less constant over time
• Populations stable around carrying capacity

Question 20

List some common features of succession

Answer 20

• Abiotic environment becomes less hostile
• Greater number of habitats and food sources
• Increase in biodiversity (peaks in mid-succession, decrease in climax community)
• More complex food webs
• Increase in biomass (peaks at climax community)

Question 21

What is secondary succession?

Answer 21

The recolonisation of an area after a community has been removed or destroyed by, for example, fire, disease or deforestation

Question 22

Why does secondary succession happen more rapidly?

Answer 22

• Spores and seeds are often in the soil
• Animals and plants from surrounding areas enter by dispersal and migration

Question 23

Define conservation

Answer 23

A method of maintaining ecosystems and the living organisms that occupy them by active human intervention

Question 24

Why does gross productivity decrease when climax community is reached?

Answer 24

• Less light
• Reduced photosynthesis