B3 Life on Earth. B3 Life on Earth. Question What is the definition of a species? Question What is classification?

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1 Q1 Q2 What is the definition of a species? What is classification? A group of organisms that can breed together and produce fertile offspring. A system used by scientists to group organisms according to similarities in their characteristics. Q3 Organisms have features that help them to survive in their environments what is the scientific term for these features? Adaptations Q4 Explain how either a polar bear or a cactus is adapted to its environment. 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.

2 Q5 Q6 How long ago did life begin on Earth? How do fossils provide evidence that we evolved from simpler life forms? About 3500 million years ago. The fossil record shows species becoming more complex with time. Q7 How do scientists use DNA evidence to show evolution? Scientists compare the similarities and differences between DNA sequences. Q8 Explain how evolution could lead to the formation of a new species. 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.

3 Q9 What are the stages in natural selection? 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. Q10 What is selective breeding? 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. Q11 Give one reason why Lamarck s theory was rejected in favour of Darwin s theory. Lamarck thought that acquired characteristics could be passed on (inherited). Q12 Describe how humans can be directly and indirectly responsible for extinction. Directly: hunting Indirectly: destroying habitat or introducing new species.

4 Q13 What are the three main reasons for a species becoming extinct. Q14 What is a mutation? Change in environmental conditions Introduction of a new species (predator, competitor, disease organism) An organism in its food web that it relies upon becomes extinct. A change in a gene (DNA). Q15 Q16 What resources do animals compete for in an environment? What is interdependence? Food, water, shelter, a mate. The way in which organisms rely on other organisms (usually for food).

5 Q17 Describe 2 ways in which energy is transferred between organisms in an ecosystem. Energy is transferred when animals eat plants and other animals. Energy is transferred when decay organisms feed on dead organisms and waste. Q18 Give three ways in which energy is removed at each stage in a food chain. 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. Q19 What is a food web? A food web shows the relationship between the food chains in a particular environment. Q20 True or False in a food web, if one organism dies out, the other organisms will not be affected. Why? 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.

6 Q21 What is the source of all the energy in a typical ecosystem? The Sun. Q22 Why is it unusual to find a food chain with more than 5 stages? 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. Q23 In the following food chain, calculate the efficiency of energy transfer between the rosebush and the greenfly. Rosebush greenfly ladybird kJ kJ 900kJ 10000kJ kj x 100 = 12.5% efficient Q24 Name two processes that release carbon dioxide into the atmosphere. Plant/animal respiration Released from decomposition Combustion of fossil fuels

7 Q25 In the carbon cycle, how is carbon dioxide turned into carbon compounds? In plants, photosynthesis converts the carbon into sugars. The carbon can then be incorporated into carbohydrates, fats and proteins. Q26 List four factors that are essential for plants to live. Light Minerals Carbon dioxide Water Q27 Q28 How is carbon dioxide removed from the atmosphere? In photosynthesis. Why are microorganisms important in the carbon cycle? When plants and animals die they are broken down by decomposers (microorganisms). They release CO 2 into the atmosphere via respiration.

8 Q29 What is nitrogen used for in the body? Q30 What is nitrogen fixation? Nitrogen is needed for making proteins for growth. When nitrogen gas from the air is turned into nitrogen compounds (e.g. nitrates) that plants can use. Q31 Q32 What is the role of denitrifying bacteria in the nitrogen cycle? What is the role of nitrifying bacteria in the nitrogen cycle. They turn nitrates back into nitrogen gas. They turn the ammonia in decaying matter into nitrates.

9 Q33 Give three examples of environmental changes that can be measured using non-living indicators. Temperature Nitrate level Carbon dioxide level Q34 Explain how mayfly nymphs can be used to measure environmental change. 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. Q35 What is biodiversity? Q36 What is a monoculture? Explain the effect of large-scale monoculture on biodiversity. Biodiversity is the variety of life on Earth and the genetic variation that it contains. 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.

10 Q37 Define sustainability. Meeting the needs of today s population without harming the environment so that future generations can still meet their own needs. Q38 Most packaging materials are thrown away, why is this not sustainable? 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. Q39 How could packaging be made more sustainable? Use renewable materials. Use less energy in production. Use biodegradable materials. Use less packaging material.