Life On Earth Flashcards
What is a species?
A group of organisms which can interbreed to produce fertile offspring
What is biodiversity?
The range of different species present in an ecosystem. The higher the biodiversity, the more species present
What is a population?
All the organisms of one species living in an area
What is a producer?
An organism which makes its own food by photosynthesis
What is a consumer?
An organism which has to eat a plant or animal to gain energy
What is a herbivore?
A consumer that eats plant material only. Herbivores are primary consumers
What is an omnivore?
A consumer that eats both plant and animal material. Omnivores can be primary or secondary consumer
What is a carnivore?
A consumer that eats animal material only. Carnivores are secondary consumers
What is a predator?
An animal which hunts, kills and feeds on another animal
What is prey?
The animal which is hunted and eaten by a predator for food
What is a food chain?
A food chain shows a simple feeding relationship between organisms
What is a food web?
A food web consists of many food chains linked together showing more complex feeding relationship in an ecosystem
What is a habitat?
The place where an organism lives
What is a community?
All the organisms living in an area
What is an ecosystem?
All the organisms living in a particular habitat and the non-living components with which the organisms interact
What do the arrows in a food chain/web show?
Direction of energy flow
What is the niche?
The role that an organism plays within its community
Why does competition occur?
When the resources required by organisms are in short supply
What do plants compete for?
Light, water, space and soil nutrients
What do animals compete for?
Food, water, space, shelter and mates
What are the two type of competition?
Interspecific, intraspecific
When does interspecific competition occur?
Occurs amongst individuals of different species for one or a few of the resources they require
When does intraspecific competition occur?
Occurs amongst individuals of the same species and is for all the resources required
What are biotic factors?
Factors caused by living organisms in an ecosystem and their interactions
Examples of biotic factors are?
Disease, predation, competition for resources, grazing and availability of food
What are abiotic factors?
Non-living factors in an ecosystem that can influence where organisms can live
Examples of abiotic factors are?
Light intensity, temperature soil moisture and soil pH
What is an indicator species?
Species that by their presence or absence indicate environmental quality and levels of pollution
What is photosynthesis?
The process by which green plants produce their own sugar
What is the word summary for photosynthesis?
Carbon dioxide+Water—————-> Sugar+Oxygen
Chlorophyll
Enzymes
Where is carbon dioxide taken in through in the leaf?
Stomata, tiny pores in the leaf
Where is water absorbed in the plant
The plants roots
Where is the main site of photosynthesis?
The palisade mesophyll
Why does the palisade mesophyll contain a greater number of chloroplasts?
To allow them to absorb more light for photosynthesis
What are the 2 stages of photosynthesis?
Light reactions and carbon fixation
Describe the stages of light reactions
1) light energy from the sun is trapped by chlorophyll in the chloroplasts and is converted into chemical energy which is used to generate ATP
2) the light energy is also used to split water into hydrogen and oxygen
3) oxygen diffuses out from the cell as a by-product
4) the hydrogen and ATP produced are passed to the second stage of photosynthesis
Describe the stages of carbon fixation
1) carbon fixation involved a series of enzyme-controlled reactions
2) hydrogen combines with carbon dioxide, which diffuses into the leaves through the stomata. This step also requires ATP
What is the chemical energy in the sugar produced during photosynthesis available for?
Respiration, or it can be converted into other substances
What other substances can the sugar produced during photosynthesis be converted into?
Starch (storage), cellulose (structural component in plant cell wall)
What is a limiting factor on the rate of photosynthesis?
A factor that prevents photosynthesis occurring at its maximum rate
Examples of limiting factors of photosynthesis are?
- light intensity
- carbon dioxide concentration
- temperature
Examples of ways to measure the rate of photosynthesis are?
- measuring the rate of uptake of carbon dioxide
- measuring the rate of production of oxygen
- measuring the mass of carbohydrate produced
What happens in transfers from one level to the next in a food chain?
The majority of the energy is lost
Reasons for energy loss are?
- movement
- heat loss
- undigested materials
What energy can be passed on and is available at the next level in the food chain?
Energy used for growth
What does a pyramid of numbers show?
The numbers of organisms present at each stage of a food chain
Why do the numbers normally decrease in a pyramid of numbers as you move up the food chain?
- energy is lost at each stage
- the size of the organism at each stage increases
What does a pyramid of energy show?
The total quantity of available energy at each level in the food chain
Why are pyramids of energy always a true pyramid?
Energy is always being lost as you move up the chain no matter what the body size of the organism is
What do fertilisers provide?
Provide chemicals, such as nitrates
What do pesticides do?
Killed plants and animals (pest species) which reduce crop yields
Where are nitrates when plants absorb them?
Dissolved in soil water
What are the nitrates absorbed by plants used for?
To produce amino acids which are synthesised into plant proteins
Describe the consequences of an Algal Bloom?
1) algal blooms reduce light levels, killing aquatic plants (as they cannot photosynthesise)
2) these dead plants, as well as dead algae become a supply of food for bacteria
3) due to this increased food supply the bacteria greatly increase in numbers
4) the bacteria then use up large quantities of oxygen, reducing the oxygen availability for other organisms
5) this can result in the death of freshwater animals and plants
What is used to reduce the use of fertilisers?
Genetically modified (GM) crops
Describe the effects of pesticides on the food chain?
1) pesticides spayed onto crops can accumulate in the bodies of organisms over time
2) as pesticides are passed along food chains, toxicity increases and can reach lethal levels
3) the build-up of toxic substances in living organisms is known as bioaccumulation
2 alternatives to using chemicals in crops are?
- genetic modification
- biological control
What is a mutation?
A random change to the genetic material of an organism
What are mutations the only source of?
New alleles
What are the 3 types of mutations?
- advantageous (increase)
- disadvantageous (decrease)
- neutral (NO change)
What can 8increase the rate of mutations?
Environmental factors
- radiation
- chemicals
What can new alleles being produced result in?
Better adapted animals and plants
What does variation which in a population mean?
Makes it possible for a population to evolve over time in response to changing environmental conditions
What is an adaption?
An inherited characteristic that makes an organism well suited to its environment, enabling it to survive in its environment/niche
What is a selection pressure?
A factor that affects a population resulting in the death of some individuals and the survival of others
What occurs when there is selection pressures?
- natural selection
- survival of the fittest
What is speciation?
The form of new species
When does speciation occur?
After part of a population becomes isolated by an isolation barrier. This prevents interbreeding and gene exchange
The three isolation barriers are?
- geographical (sea, mountains)
- ecological (pH, different habitats)
- behavioural (reproductive nature)
What are the three steps in speciation?
- isolation
- mutations in each sub population
- natural selection
