Ecosystems

Question 1

Define ecosystem

Answer 1

All living organisms in an area interacting with non-living (abiotic) factors

Question 2

Define habitat

Answer 2

The area an organism lives

Question 3

Define population

Answer 3

Number of organisms of a species in a particular habitat

Question 4

Define community

Answer 4

All organisms of different species that live and interact in the same arra

Question 5

Define abiotic and biotic factors

Answer 5

Abiotic - Non-living
Biotic - Living

Question 6

Give examples of abiotic factors

Answer 6

Sunlight, CO2, O2, water, space, temperature

Question 7

Why is it important for abiotic factors to remain constant?

Answer 7

Must be ideal to maintain abundance; means species can grow and reproduce successfully —> if not ideal more energy is used for survival so less available for growth + reproduction

Question 8

Define the three types of biotic factors

Answer 8

• Interspecific competition —> when organisms from different species compete for the same resources
• Intraspecific competition —> when members of the same species compete for resources
• Predation —> interaction between predator and prey

Question 9

How does number of organisms in a species change over time?

Answer 9

1 Resources plentiful, population increases, so more competition for food and space
2 Food and space limited; not enough for organisms so population falls
3 Reduced population means more food + space available allowing population to increase
Cycle continues around carrying capacity —> maximum abundance of a species that is stable which an ecosystem can support

Question 10

How does number of predators and prey change over time?

Answer 10

1 Prey population increases; more food for predators so predator pop increases
2 As the predator pop increases, more prey is eaten so prey pop begins to fall
3 Means less food for predators; predator pop decreases and so on

Question 11

How may abiotic and biotic factors affect distribution?

Answer 11

Abiotic = e.g. shade affecting where plants grow, plants on seashore thrive in salty conditions
Biotic = Interspecific competition —> better adapted species will survive and reproduce, increasing pop size and other species may disappear

Question 12

What niche can be in abiotic and biotic factors?

Answer 12

Biotic interactions —> what the species eats and what eats it
Abiotic interactions —> oxygen it breathes and CO2 it breathes out

Question 13

Define succession

Answer 13

Gradual change in a community over time

Question 14

Define primary and secondary succession

Answer 14

Primary - occurs when organisms colonise
Secondary - occurs when organisms recolonise a devastated ecosystem

Question 15

Describe the stages of primary succession

Answer 15

1 Pioneer phase —> Pioneer species (first species to colonise area)
- usually plants with adaptions to survive in harsh/extreme conditions
-also have adaptations like seeds being widely dispersed by wind, rapid growth, short life cycle, abundant seed production
2 Pioneer species breaks up rock surface; death/decomposition accumulates organic matter, forming soil
3 Wind/blown moss spores grow; organic matter and roots bind soil, resulting water retention
4 Soil quality improves; larger and taller plants colonise
5 New species outcomes pre existing ones
6 This happens until climax community is reached with dominant species (often trees)

Question 16

Describe stages of secondary succession

Answer 16

~ A pre established climax community is destroyed by natural disaster or human activity
~ restart of succession process occurs in this area
~ Undisturbed, results in the same climax community
- Quicker than primary as it skips steps, soil is already good quality