10.1- the nature of ecosystems

Question 1

habitat definition

Answer 1

the area or natural environment in which an organism or population normally lives

Question 2

ecosystem definition

Answer 2

a biological community of organisms which interact with each other and their physical environment

Question 2

community definition

Answer 2

all the organisms present in an ecosystem at a given time

Question 2

population definition

Answer 2

a group of individuals of the same species that occupy the same habitat at the same time

Question 3

niche definition

Answer 3

a term for the position of a species within an ecosystem

Question 4

biome definition

Answer 4

a specific environment that’s home to living things suited for that place and climate e.g. desert or tropical rainforest

Question 5

biodiversity

Answer 5

the number and variety of living organisms in the living world

Question 6

what are abiotic factors

Answer 6

-non living elements of a habitat or organism

Question 7

abiotic factors example

Answer 7

-air
-water
-light
-wind
-soil
-pH
-temp
-humidity
-inorganic nutrients

Question 8

what are biotic factors

Answer 8

-the living elements of a habitat that affect the ability of a group of organisms to survive there

Question 9

biotic factors examples

Answer 9

-other organisms so..
-competition
-predation
-symbiosis (mutualism and parasitism)
-disease agents

Question 10

climatic abiotic factors

Answer 10

-factors include humidity, sunlight and factors involving the climate

Question 11

edaphic abiotic factors

Answer 11

-soil conditions, so edaphic abiotic factors include soil and geography of the land

Question 12

topographic abiotic factors

Answer 12

-physical features of an area including height, direction of slope and steepness of slope

Question 13

what is succession

Answer 13

-the process of a community changing over time
-heavily influenced by conditions in the environment

Question 14

how does succession happen

Answer 14

-community consists of all plants and animals in particular area
-individual populations in a community interact
-the community is constantly changing and dynamic, which passes through a number of stages from origin to climax
-transition from one stage to next is succession

Question 15

primary succession

Answer 15

-progressive colonisation of bare rock or barren terrain by living organisms

Question 16

secondary succession

Answer 16

-the recolonization of an area after an earlier community has been removed or destroyed

Question 17

primary succession in steps

Answer 17

-pioneer species begins breaking down rock
-lichens usually grow on rock
-Lichens secrete acids that begin breaking rock into small particles
-more complex plants grow when soil is deep enough
-eventually succeeds lichens
-organic material can hold water
-larger complex plants
-forests if soil deep enough
-Climax community
Is very stable and can endure for hundreds of years.

Question 18

overall features that emerge in succession

Answer 18

-The abiotic environment becomes less hostile (e.g. soil forms).
-More complex food webs.
-Increased biomass.
-Increased biodiversity – increase in number of species.
-Greater number and variety of habitats and niches.

Question 19

succession stages summarised

Answer 19

-grassland, small flowering plants
-tall herbaceous plants
-bushes and shrubs
-fast growing trees
-larger, slower growing strong trees

Question 20

summary of succession (mark scheme)

Answer 20

1.Pioneer species/mosses/lichens arrive
2.decomposition increases the soil depth and mineral/nutrient content.
3.Therefore larger plants can grow.
4.More herbaceous plants/shrubs/trees are present.
5.Nitrate content in soil grows as there are more leaves/plants/animals/faeces.
6.Climax community emerges at end.

Question 21

where does secondary succession take place

Answer 21

areas where life is already present but has been altered in some way
-faster than primary

Question 22

3 main causes of secondary succession

Answer 22

1.natural catastrophe (fire)
2.human destruction
3.human management (ploughing)

Question 23

2 main ways of sampling

Answer 23

-systematic
-random

Question 24

random sampling

Answer 24

-used in large area which is very uniform
1.numbered grid- lay grid over, random number generator
2.random walk-Each sample point is located by taking a random number between 0 and 360, to give a compass bearing, followed by another random number which indicates the number of paces which should be taken in that direction.

Question 25

how to use quadrats

Answer 25

-only count if plant mostly in
-if large abundance, count percentage cover

Question 26

systematic sampling

Answer 26

-used to see change in species
-lay transect, record at regular intervals
-stop when there’s no further change

Question 27

sampling techniques

Answer 27

-pitfall trap
-tullgren funnel
-beating tray
-pooter
-kick net
-sweep net

Question 28

abiotic factors- light

Answer 28

-needed for photosynthesis
-at low light intensity plants may have extra chlorophyll
-Animals are sensitive to light level indirectly as a result of the distribution of food plants.

Question 29

abiotic factors-temperature

Answer 29

-extremes of temp determine whether organisms can live
-temp controls rate of enzyme controlled reactions

Question 30

abiotic factors- wind/water

Answer 30

-wind can inc water loss from body, cooling
-in currents organisms must be able to;
-be strong swimmers
-attach to surface or
-flow with current

Question 31

abiotic factors- water availability

Answer 31

-effected by amount of rainfall, rate of evaporation and rate of soil drainage

Question 32

abiotic factors- oxygen

Answer 32

-in water or soil
-if soil is water logged there may be a lack of oxygen

Question 33

how does competition occur

Answer 33

-when 2 or more organisms share resources that is insufficient to satisfy them fully

Question 34

intraspecific competition

Answer 34

-when individuals in the same species compete for resources
-availability of resources determine size of population
-larger availability= larger population

Question 35

interspecific competition

Answer 35

-when individuals in different species compete for resources
-usually one has a competitive advantage
-could lead to removal of one species
-known as competitive exclusion principle

Question 36

biotic factors- predation

Answer 36

-populations where predation in present will oscillate in repeating cycles
-because as prey increases there is more food for predators
-pred population inc until the point where they are eatinf more than they produce, so not enough food for offspring so numbers decrease

Question 37

biotic factors- finding a mate

Answer 37

-single organisms cannot populate an entire habitat
-organisms must have mates to reproduce

Question 38

biotic factors- territory

Answer 38

-A territory is an area held and defended by an animal or group of animals against other organisms.
- ensure that a breeding pair has sufficient resources to raise their young.
-Territory type and size of a territory helps to determine which species can live there.

Question 39

biotic factors- parasitism and disease

Answer 39

-diseased animals cannot reproduce successfully
-sick predators cannot hunt
-parasites effect hosts by feeding on them and therefore weakening them
-spread more rapidly in high population
-fewer effects if biodiversity is high

Question 40

density dependent limiting factors

Answer 40

-factors which depend on population size
e.g. competition, food and disease

Question 41

density independent limiting factors

Answer 41

-affect all populations in similar way regardless of population size
-e.g. hurricanes or wild fire

Question 42

human influence on ecosystems

Answer 42

-humans take resources from biosphere
-as human population grows so does the resources we take for food medicine and shelter
-the waste we create can also effect organisms