unit 3

Question 1

what is an ecosystem

Answer 1

consists of all the organisms (the community) living in a particular habitat and the non-living components with which they interact

Question 2

what is a species

Answer 2

group of organisms which can interbreed to produce fertile offspring

Question 3

what is a population?

Answer 3

number of organisms within a particular species

Question 4

what is biodiversity

Answer 4

variety of life within an ecosystem

Question 5

what is a community?

Answer 5

all the organisms that live within a habitat or ecosystem

Question 6

what is a habitat

Answer 6

the place where an organism lives

Question 7

what is a food chain

Answer 7

a series of organisms which can depend on each other for food (energy)

Question 8

what’s a herbivore?

Answer 8

an animal which consumes only plants to gain energy

Question 9

what’s a omnivore?

Answer 9

an animal that consumes both plants and animals to gain energy

Question 10

what’s a carnivore

Answer 10

an animal that consumes other animals to gain energy

Question 11

producer:

Answer 11

any green plant that makes its own food via photosynthesis

Question 12

consumer:

Answer 12

an animal that consumes plants or other animals for energy

Question 13

prey:

Answer 13

animals who are hunted by predators

Question 14

predator:

Answer 14

hunts prey to gain energy

Question 15

food web:

Answer 15

a diagram which shows the interconnection of food chains and the feeding relationship in an ecosystem

Question 16

niche:

Answer 16

role an organism plays within its community

Question 17

interspecific competition:

Answer 17

individuals of different species competing for one or a few resources they require

Question 18

intraspecific competition:

Answer 18

individuals of the same species and is for all resources required

Question 19

biotic:

Answer 19

living factor which affects biodiversity
eg competition, predation, grazing, disease

Question 20

abiotic:

Answer 20

non-living factor which affects biodiversity
eg temperature, pH, soil moisture, light intensity

Question 21

quadrats:

Answer 21

used to estimate the number of plants or slow moving animals of a particular type in an area

Question 22

errors of quadrats and how to minimise

Answer 22

not enough placed - place more

some plants may be partially in or out - decide how ur going to sample

biased - throw randomly

Question 23

pitfall traps:

Answer 23

use to sample invertebrates which live on the ground

Question 24

errors of pitfall traps and how to minimise

Answer 24

not enough to represent ecosystem - place more traps

some animals eaten by predators - check regularly

water filling in trap - drainage holes

Question 25

indicator species:

Answer 25

species that by their presence or absence indicate environmental quality/levels of pollution

Question 26

how is energy lost in a food chain

Answer 26

- heat - undigested materials - movement

Question 27

pyramid of energy

Answer 27

shows the energy available at each link in food chain

Question 28

pyramid of numbers

Answer 28

diagram that shows the total number of organisms at each link in food chain

Question 29

photosynthesis:

Answer 29

reaction that converts light energy into chemical energy. during photosynthesis light energy along with carbon dioxide and water are used to produce sugar and oxygen

Question 30

word equation:

Answer 30

light energy CO2 + H2O —————-> sugar + O2

Question 31

light reactions:

Answer 31

light energy from the sun is trapped by a green pigment called chlorophyll in the chloroplast. the light energy is converted into chemical energy which generates ATP. water is split into hydrogen and oxygen during the light reactions. the hydrogen is used in the second stage and the oxygen diffuses from the cell

Question 32

carbon fixation:

Answer 32

CF uses hydrogen and ATP from the 1st stage to convert carbon dioxide form the air into sugar. this stage is catalysed by enzymes : affected by temp

Question 33

fates:

Answer 33

- sugar converts into starch (storage) - sugar converts into cellulose ( structural) - sugar is available for respiration (glucose)

Question 34

limiting factors of photosynthesis

Answer 34

- temp - light intensity - carbon dioxide concentration

Question 35

fertiliser:

Answer 35

added to soil to increase nitrate content of soil to increase crop yield

Question 36

what is GM crops

Answer 36

involves inserting DNA into the genome of an organism to give it new or different characteristics helps to maintain crop yield

Question 37

bioaccumulation:

Answer 37

the build up of toxic substances in living organisms

Question 38

pesticide:

Answer 38

substance used to kill insects which destroy the crop

Question 39

biological control:

Answer 39

controlling pest numbers by introducing a natural predator

Question 40

mutation:

Answer 40

random change to genetic material, they can be neutral, advantageous or disadvantageous to survive - mutations are spontaneous and are the only source of new alleles

Question 41

mutagenic agent:

Answer 41

environmental factors which increase the rate of mutation eg extreme temp, radiation and chemicals

Question 42

adaptation:

Answer 42

inherited characteristic that makes an animal/plant well suited to its environment

Question 43

variation within a population makes it possible for…

Answer 43

… a population to evolve over time in response to changing environmental conditions

Question 44

selection pressures of natural selection:

Answer 44

food predation climate disease

Question 45

natural selection:

Answer 45

1. species produce more offspring than the environment can sustain 2. when there are selection pressures, the best adapted individuals survive to reproduce, passing on the favourable alleles that confer the selective advantage 3. these alleles increase in frequency within the population 4. this can result in a population becoming better adapted to its ecological niche

Question 46

speciation (simple definition)

Answer 46

formation of a new species

Question 47

isolation barriers:

Answer 47

- geographical barriers = physically separating groups within a population eg rivers or mountains - behavioural barriers = separating populations because of behaviour of individuals eg females selecting for a different male characteristic during mating season - ecological barriers = separating populations due local differences in the environment eg pH or salinity

Question 48

stages of speciation:

Answer 48

1. isolation by barrier - speciation occurs after part of a population becomes isolated by an isolation barrier (ecological, behavioural or geographical) 2. different mutations occur randomly in the each sub population causing new variation 3. natural selection selects for different mutations in each group, due to different selection pressures 4. each sub-population evolves until they become so genetically different that they are 2 different species (they can’t interbreed and produce fertile offspring)

Question 49

why can’t photosynthesis occur at very high temps?

Answer 49

because enzyme activity is lower

Question 50

what are nitrates?

Answer 50

they are the type of chemical found in fertilisers that plants use to make amino acids

Question 51

speciation (simple steps)

Answer 51

1. isolation barriers 2. mutations in each sub-population 3. natural selection 4. evolve into different species

Question 52

why does natural selection ensure the most favourable alleles are passed on?

Answer 52

because the species with the favourable alleles survive as they are more adapted

Question 53

products of light reactions:

Answer 53

hydrogen and oxygen