b3 – life on earth question answer · a group of organisms that can breed together and produce...

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?


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.


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?


Q3

Answer:Adaptations

QuestionHow long ago did life begin on Earth?


Q5

Answer:About 3500 million years ago.

QuestionHow do fossils provide evidence that we evolved from simpler life forms?


Q6

Answer:The fossil record shows species becoming more complex with time.

QuestionExplain how evolution could lead to the formation of a new species.


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?


Q7

Answer:Scientists compare the similarities and differences between DNA sequences.

QuestionWhat are the stages in natural selection?


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?


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.


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.


Q11

Answer:Lamarck thought that acquired characteristics could be passed on (inherited).

QuestionWhat are the three main reasons for a species becoming extinct.


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?


Q14

Answer:A change in a gene (DNA).

QuestionWhat resources do animals compete for in an environment?


Q15

QuestionWhat is interdependence?


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?


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?


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.


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.


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.


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


Q23

Answer:10000kJ ÷ 80000 kJ x 100 = 12.5% efficient

QuestionWhat is the source of all the energy in a typical ecosystem?


Q21

Answer:The Sun.

QuestionWhy is it unusual to find a food chain with more than 5 stages?


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?


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.


Q26

Answer:LightMineralsCarbon dioxideWater

QuestionHow is carbon dioxide removed from the atmosphere?


Q27

Answer:In photosynthesis.

QuestionWhy are microorganisms important in the carbon cycle?


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?


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?


Q29

Answer:Nitrogen is needed for making proteins for growth.

QuestionWhat is the role of denitrifying bacteria in the nitrogen cycle?


Q31

Answer:They turn nitrates back into nitrogen gas.

QuestionWhat is the role of nitrifying bacteria in the nitrogen cycle.


Q32

Answer:They turn the ammonia in decaying matter into nitrates.

QuestionExplain how mayfly nymphs can be used to measure environmental change.


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.


Q33

Answer:TemperatureNitrate levelCarbon dioxide level

QuestionWhat is a monoculture? Explain the effect of large-scale monoculture on biodiversity.


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?


Q35

Answer:Biodiversity is the variety of life on Earth and the genetic variation that it contains.

QuestionDefine sustainability.


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?


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?


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.

b3 – life on earth question answer · a group of organisms that can breed together and produce...

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