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QuestionWhat is the definition of a species?
B3 – Life on Earth
Q1
Answer:A group of organisms that can breed together and produce fertile offspring.
QuestionWhat is classification?
B3 – Life on Earth
Q2
Answer:A system used by scientists to group organisms according to similarities in their characteristics.
QuestionExplain how either a polar bear or a cactus is adapted to its environment.
B3 – Life on Earth
Q4
Answer:Polar bear: black skin to absorb heat;, thick fur/blubber for insulation; white appearance as camouflage from prey.Cactus: Thick waxy layer and leaves reduced to spines to conserve water; shallow but extensive roots; store water in thick stem.
QuestionOrganisms have features that help them to survive in their environments – what is the scientific term for these features?
B3 – Life on Earth
Q3
Answer:Adaptations
QuestionHow long ago did life begin on Earth?
B3 – Life on Earth
Q5
Answer:About 3500 million years ago.
QuestionHow do fossils provide evidence that we evolved from simpler life forms?
B3 – Life on Earth
Q6
Answer:The fossil record shows species becoming more complex with time.
QuestionExplain how evolution could lead to the formation of a new species.
B3 – Life on Earth
Q8
Answer:If groups of organisms in the same species are separated so that they don’t interbreed, different mutations could arise in each group. These mutations could create different features. Over time, natural selection would act on the new features so that any of benefit would spread through the population.
QuestionHow do scientists use DNA evidence to show evolution?
B3 – Life on Earth
Q7
Answer:Scientists compare the similarities and differences between DNA sequences.
QuestionWhat are the stages in natural selection?
B3 – Life on Earth
Q9
Answer:• Living things show variation.• Individuals compete for resources.• Some varieties of a species have a
better chance of survival.• This increases their chances of
reproducing and passing on their genes.
• A greater proportion of the next generation will have the characteristics to help them survive.
QuestionWhat is selective breeding?
B3 – Life on Earth
Q10
Answer:Selective breeding involves humans deliberately choosing a feature that they want to appear in the next generation and only breeding from organisms that have it.
QuestionDescribe how humans can be directly and indirectly responsible for extinction.
B3 – Life on Earth
Q12
Answer:Directly: huntingIndirectly: destroying habitat or introducing new species.
QuestionGive one reason why Lamarck’s theory was rejected in favour of Darwin’s theory.
B3 – Life on Earth
Q11
Answer:Lamarck thought that acquired characteristics could be passed on (inherited).
QuestionWhat are the three main reasons for a species becoming extinct.
B3 – Life on Earth
Q13
Answer:Change in environmental conditionsIntroduction of a new species (predator, competitor, disease organism)An organism in its food web that it relies upon becomes extinct.
QuestionWhat is a mutation?
B3 – Life on Earth
Q14
Answer:A change in a gene (DNA).
QuestionWhat resources do animals compete for in an environment?
B3 – Life on Earth
Q15
QuestionWhat is interdependence?
B3 – Life on Earth
Q16
Answer:The way in which organisms rely on other organisms (usually for food).
Answer:Food, water, shelter, a mate.
QuestionWhat is a food web?
B3 – Life on Earth
Q19
Answer:A food web shows the relationship between the food chains in a particular environment.
QuestionTrue or False – in a food web, if one organism dies out, the other organisms will not be affected. Why?
B3 – Life on Earth
Q20
Answer:False. Organisms in a food web are dependent on one another, if one of them is removed this can lead to an increase/decrease in the population of other species.
QuestionDescribe 2 ways in which energy is transferred between organisms in an ecosystem.
B3 – Life on Earth
Q17
Answer:Energy is transferred when animals eat plants and other animals.Energy is transferred when decay organisms feed on dead organisms and waste.
QuestionGive three ways in which energy is removed at each stage in a food chain.
B3 – Life on Earth
Q18
Answer:• Used for life processes e.g. respiration.• To the surroundings as heat.• As waste products e.g. faeces and urine.• Uneaten parts of organisms e.g. bones.
QuestionName two processes that release carbon dioxide into the atmosphere.
B3 – Life on Earth
Q24
Answer:• Plant/animal respiration• Released from decomposition• Combustion of fossil fuels
QuestionIn the following food chain, calculate the efficiency of energy transfer between the rosebush and the greenfly.
Rosebush greenfly ladybird 80 000kJ 10 000kJ 900kJ
B3 – Life on Earth
Q23
Answer:10000kJ ÷ 80000 kJ x 100 = 12.5% efficient
QuestionWhat is the source of all the energy in a typical ecosystem?
B3 – Life on Earth
Q21
Answer:The Sun.
QuestionWhy is it unusual to find a food chain with more than 5 stages?
B3 – Life on Earth
Q22
Answer:Food chains are inefficient, so much energy is removed at each stage that there is not enough left to support more organisms further up the chain.
QuestionIn the carbon cycle, how is carbon dioxide turned into carbon compounds?
B3 – Life on Earth
Q25
Answer:In plants, photosynthesis converts the carbon into sugars. The carbon can then be incorporated into carbohydrates, fats and proteins.
QuestionList four factors that are essential for plants to live.
B3 – Life on Earth
Q26
Answer:LightMineralsCarbon dioxideWater
QuestionHow is carbon dioxide removed from the atmosphere?
B3 – Life on Earth
Q27
Answer:In photosynthesis.
QuestionWhy are microorganisms important in the carbon cycle?
B3 – Life on Earth
Q28
Answer:When plants and animals die they are broken down by decomposers (microorganisms). They release CO
2
into the atmosphere via respiration.
QuestionWhat is nitrogen fixation?
B3 – Life on Earth
Q30
Answer:When nitrogen gas from the air is turned into nitrogen compounds (e.g. nitrates) that plants can use.
QuestionWhat is nitrogen used for in the body?
B3 – Life on Earth
Q29
Answer:Nitrogen is needed for making proteins for growth.
QuestionWhat is the role of denitrifying bacteria in the nitrogen cycle?
B3 – Life on Earth
Q31
Answer:They turn nitrates back into nitrogen gas.
QuestionWhat is the role of nitrifying bacteria in the nitrogen cycle.
B3 – Life on Earth
Q32
Answer:They turn the ammonia in decaying matter into nitrates.
QuestionExplain how mayfly nymphs can be used to measure environmental change.
B3 – Life on Earth
Q34
Answer:Mayfly nymphs are a good indicator for water pollution as they are sensitive to the level of oxygen in the water. Clean water has more oxygen as bacteria are not using it up. If mayfly nymphs are in the water then this indicates that it is clean.
QuestionGive three examples of environmental changes that can be measured using non-living indicators.
B3 – Life on Earth
Q33
Answer:TemperatureNitrate levelCarbon dioxide level
QuestionWhat is a monoculture? Explain the effect of large-scale monoculture on biodiversity.
B3 – Life on Earth
Q36
Answer:A monoculture is just one type of crop (genetically identical). It will support fewer species than a field containing lots of different species. A monoculture is also more likely to be wiped out by pests or disease.
QuestionWhat is biodiversity?
B3 – Life on Earth
Q35
Answer:Biodiversity is the variety of life on Earth and the genetic variation that it contains.
QuestionDefine sustainability.
B3 – Life on Earth
Q37
Answer:Meeting the needs of today’s population without harming the environment so that future generations can still meet their own needs.
QuestionHow could packaging be made more sustainable?
B3 – Life on Earth
Q39
Answer:• Use renewable materials.• Use less energy in production.• Use biodegradable materials. • Use less packaging material.
QuestionMost packaging materials are thrown away, why is this not sustainable?
B3 – Life on Earth
Q38
Answer:The resources that have gone into making the packaging material are not re-used, so no longer available.Lots of energy is used in their production.Waste thrown on landfill sites takes up space and damages the environment.
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