Ecosystems

Question 1

what is an ecosystem?

Answer 1

made up of all living organisms that interact in a defined area, and the physical factors present. they can vary in size and are dynamic.

Question 2

what is a biotic factor?

Answer 2

living factors.
e.g. predators, competition, mutualism/parasitism

Question 3

what is an abiotic factor?

Answer 3

non living factors
e.g. temperature, water, humidity, light, wind, carbon dioxide

Question 4

why do abiotic factors often have a bigger effect on plants than animals in an ecosystem?

Answer 4

plants are unable to hide / shelter / migrate in extreme conditions
plants are more reliant on light/water in order to photosynthesise
animals can regulate internal body temp

Question 5

what is a species?

Answer 5

organisms with similar features which reproduce to produce fertile offspring

Question 6

what is a population?

Answer 6

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

Question 7

what is a community?

Answer 7

all populations of different species living in the same place at the same time

Question 8

what is a biome?

Answer 8

a large scale ecosystem defined by abiotic factors such as weather

Question 9

what is a biosphere?

Answer 9

an area of the planet where organisms live, including the ground, water and air

Question 10

why are ecosystems dynamic but stable?

Answer 10

population sizes rise and fall due to interactions between organisms and the environment. any small change can affect the other in predator/prey relationships

Question 11

what does niche mean?

Answer 11

the role of an organism in its ecosystem e.g where it lives

Question 12

what does habitat mean?

Answer 12

the place where an organism/community lives

Question 13

what is a keystone species?

Answer 13

• significant effect on ecosystem
• could be relied on by other organisms

Question 14

what is a dynamic ecosystem?

Answer 14

constantly changes over time

Question 15

what is a trophic level?

Answer 15

each stage in a food chain

Question 16

what are food chains/webs used to demonstrate?

Answer 16

transfer of biomass (energy) through organisms in an ecosystem

Question 17

describe the first trophic level

Answer 17

producer - an organism that converts light energy into chemical energy via photosynthesis

Question 18

why is there a limited number of trophic levels?

Answer 18

there is not sufficient biomass and stored energy left to support further organisms

Question 19

what is the role of decomposers?

Answer 19

break down dead organisms and release nutrients back into the ecosystem

Question 20

what is ‘biomass’?

Answer 20

the mass of living material present in a particular place or organisms

Question 21

how would you calculate the biomass at each trophic level?

Answer 21

biomass present x total number of organisms in trophic level

Question 22

what is meant by ‘ecological efficiency’?

Answer 22

the efficiency by which biomass/energy is transferred

Question 23

what makes up the biomass?

Answer 23

cells and tissues composed of carbon compounds

Question 24

what are units for biomass on land and water?

Answer 24

land = gm-2
water = gm-3

Question 25

how is biomass measured?

Answer 25

discount water and measure the mass

Question 26

why is it important to not consider the water and use dry mass?

Answer 26

organisms have varied amounts of water

Question 27

what are the limitations of pyramids of biomass?

Answer 27

fails to consider how climate plays a role in trophic level activities

Question 28

how are biomass and energy linked?

Answer 28

light energy is captured by plants and transferred to organic compounds, forming biomass. - therefore biomass can be equated to energy content

Question 29

what is meant by gross primary production?

Answer 29

the rate at which chemical energy is stored by producers