succession

Question 1

define succession

Answer 1

long term directional change from bare inorganic surfaces to plant communities to a climax community over time

Question 2

how does succession change organisms

Answer 2

changes in abiotic factors change the plants and animals present

Question 3

define primary succession

Answer 3

occurs on an area of land that has been newly formed or exposed such as bare rock

Question 4

define secondary succession

Answer 4

occurs on area of land where soil is present but no plant or animal species eg. bare earth after forest fire

Question 5

define deflected succession

Answer 5

when human activity halts the natural flow of succession

Question 6

define sere / seral stage

Answer 6

a stage of change

Question 7

what is the first seral stage?

Answer 7

pioneers
- often lichen/algae
- highly adapted: germinate rapidly, photosynthesise, tolerate extreme environments, can fix nitrogen from soil
- spores / seeds carried by wind

Question 8

what is the second seral stage?

Answer 8

intermediate
- rock surface weathers
- pioneers die and are released as humus
- organic material is formed

Question 9

define pioneer species

Answer 9

organisms that colonise an inhospitable environment

Question 10

what is the third seral stage?

Answer 10

climax community:
- community is in stable state, - very little change over time
- few dominant plant and animal species

Question 11

what are secondary colonisers?

Answer 11

mosses
- sometimes animals can colonise

Question 12

what are tertiary colonisers?

Answer 12

grasses
- can survive in conditions without abundance of water
- adapted to reduce water loss

Question 13

define plagioclimax

Answer 13

final stage formed when succession is stopped artificially

Question 14

give 5 adaptations that some species have for being pioneer species.

Answer 14

• ability to produce large quantities of seeds/spores that are blown by wind and deposited on new land
• seeds that germinate rapidly
• ability to photosynthesise to produce own energy
• tolerance to extreme environments
• ability to fix nitrogen from atmosphere + adding to the mineral content of the soil

Question 15

describe the pioneer effect species have on the environment

Answer 15

• when pioneer species die and decompose, small organic products are released into soil
• organic component of soil - humus
• soil becomes able to support growth of new plant species bc it contains minerals (nitrates & ability to retain water)

Question 16

explain why secondary succession is more likely to occur than primary succession?

Answer 16

organisms develop more quickly because of nutrients present in soil whereas in primary, there was little/none

Question 17

give 3 reasons deflected succession may occur

Answer 17

• grazing and trampling of vegetation by domesticated animals
• removing existing vegetation to plant crops - crop becomes final community
• burning as a means of forest clearance