national 5 biology unit 3

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53 Terms

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species

a group of similar organisms which can produce fertile offspring

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biodiversity

variety of species living in a habitat

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producer

organisms which produce their own food

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consumer

organisms which rely on eating other organisms for food

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carnivore

meat eater

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herbivore

plant eater

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omnivore

plant and animal eater

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prey

an organism which is hunted

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predator

an organism which hunts for food

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food chain

feeding relationships between a producer and a top consumer

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food web

a network of interconnected food chains in a habitat

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ecosystem

all the organisms living in a habitat and the non living components which the organisms interact with

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niche

the role that an organism plays in a community

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a niche describes

- the resources the organism uses in an ecosystem
- the interactions an organism has in the community competition
- the conditions it can tolerate (temperature)

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competition in ecosystems occur when

resources are in short supply

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interspecific competition

when individuals of different species compete for one or a few of the resources they require

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intraspecific competition

when individuals of the same species compete for all resources they require

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biotic factors

competition for resources, disease, food availability, grazing, and predation

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abiotic factors

non living - temperature, pH, light intensity, and moisture

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photosynthesis equation

carbon dioxide + water -chlorophyll-> glucose + oxygen

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stages of phtosynthesis

light reactions and carbon fixation

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light reactions

- light energy from the sun is trapped by the chlorophyll in the chloroplasts and is converted into chemical energy which makes ATP
- water is split into hydrogen + oxygen, excess oxygen diffuses out of the leaf

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carbon fixation

- series of enzyme controlled reaction using hydrogen
- carbon dioxide combines with hydrogen to form glucose
- ATP provides energy for this from light reactions
- glucose can be used for respiration

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limiting factors of photosynthesis

temperature, light intensity, carbon dioxide

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x% amount of energy is transferred between levels in food chains

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a small quantity of energy is

used for growth

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pyramids of energy show

energy produced at each trophic level

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reason for pyramid shape

lots of energy produced by producers over a period of time

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pyramids of numbers show

total amount of organisms present in a food chain

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reason for irregularities in shape

very large oak tree and smaller herbivores

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increasing human population requires

increased food yield

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fertilisers provides nitrates to soil to

increase crop yields

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nitrates in food production

- nitrates dissolved in soil water are absorbed into plants
- nitrates produce amino acids which are synthesised into plant proteins
animals consume plants or other animals to get amino acids for protein synthesis
- fertilisers can be added to soil to increase the nitrate content of the soil

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consequences of the use of fertilisers

- fertilisers leach into freshwater adding unwanted nitrates
- increased algae populations causing algae blooms which kill aquatic plants
- dead plants and algae become food for bacteria
- bacteria use up lots of oxygen, reducing availability for other organisms

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what reduces use for fertilisers

GM crops

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pesticides can be used to kill off

plants and animals reducing crop yields

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as pesticides are passed along food chains

toxicity increases and can become lethal

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alternatives to the use of pesticides

GM crops and biological control

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mutation is

a random change to genetic material

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neutral mutations are

neither beneficial or harmful to organisms

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advantageous mutations improve

chance of survival

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disadvantageous mutations decrease

selective advantage

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mutations are

spontaneous and the only source of new alleles

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what increases rate of mutation

radiation and some chemicals

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new alleles produced by mutation results in

plants and animals becoming better adapted to their environment

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how does a population evolve over time in response to changing enviornmental conditions

variation within a population

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species produce more?

offspring than the environment can sustain

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natural selection of the fittest occurs when

there are selection pressures

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only best adapted individuals

survive to reproduce to pass on favourable alleles to pass on the selective advantage. these alleles increase in frequency within the population

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speciation occurs after

a population becomes isolation by an isolation barrier

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types of isolation barriers

geographical, ecological, or behavioural

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natural selection selects

for different mutations in each group due to different selection pressures

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each sub population evolves until

their genetic differences make them two different species