GCSE Biology B3 (OCR)

Frage	Antworten
What is a a species?	A group of organisms that can breed together to produce fertile offspring.
Why is adaptation beneficial?	It increases a species' chances of survival by making it more likely that individuals will survive to reproduce.
How are some organisms adapted to their environment? How do these adaptations help the species to survive?	Camels: Store fat in humps to make water. Not impacted by lack of water in habitats. Saguaro Cactus: Stem is pleated so that it can expand and hold more water. Canadian Lynx: Long legs and fury feet which work like snow shoes.
What do living organisms depend on for their survival?	Their environment and other species.
How may an environment change, causing a species to become extinct?	a) The conditions change beyond its ability to adapt. b) A new species that is a predator, competitor, or disease organism is introduced. c) Another species in its food web becomes extinct.
What are most organisms dependent on?	Energy from the sun.
When plants absorb energy from the Sun for photosynthesis, where is it stored?	In chemicals which make up the plant's cells.
How is energy transferred between organisms in an ecosystem?	a) When organisms are eaten b) When dead organisms and waste materials are fed on by decay organisms (decomposes and detritivores).
How does energy pass out of a food chain?	a) It is used for life processes in the organism, such as movement. b) It escapes into the environment as heat energy. c) It is excreted as waste and passes to decomposers. d) It cannot be eaten and passes to decomposers.
How do you calculate the percentage efficiency of energy transfer?	100 / Original Energy x New Energy
How is carbon recycled through the environment?	- Carbon Dioxide is taken out of the atmosphere by photosynthesis. The carbon is used to produce glucose molecules. The glucose is broken down during respiration, which releases carbon dioxide back into the atmosphere. - When an organism dies, its organic compounds are broken down by microorganisms (decomposition). The carbon becomes part of a new organism in the system. - Carbon Dioxide is added to the atmosphere by combustion (burning) of wood and fossil fuels.
Explain what happens when nitrogen compounds are converted to proteins.	Plants take up nitrates to make proteins. Herbivore animals eat plants, digest the plant proteins, and use the products (amino acids) to make their own animal proteins.
How are nitrogen compounds transferred through food chains?	When an organisms feeds off another organism, the nitrogen compounds are passes from he prey to the predator.
How are nitrates released into the soil?	Excretion, death, and decay of plants and animals leads to decomposer bacteria breaking down the proteins. This releases nitrates back into the soil for plants to absorb again. - Denitrifying bacteria break down nitrates in the soil and release nitrogen gas back into the air. This is called denitirification.
What is nitrogen fixation?	Nitrogen fixing bacteria turn nitrogen gas into nitrogen compounds (eg. nitrates). This is called nitrogen fixation.
How can environmental change be measured using non-living indicators?	- Measuring nitrate levels allows water quality to be monitored. - Measuring temperature allows global warming to be monitored. - Measuring Carbon Dioxide levels allows pollution to be monitored.
How can environmental change be measured using living indicators?	- Mayfly larvae cannot survive in water with a high nitrate concentration. - Some species of lichens only grow in areas with high nitrate levels, while others only grow in places with no air pollution.
When did life on Earth begin?	Approximately 3500 million years ago
What did life on Earth evolve from?	Very simple living things.
What is genetic variation the results of?	Changes that occur in genes (mutations).
How can new characteristics be passed on?	Mutated genes in sex cells can be passed on to offspring, and may occasionally produce new characteristics.
How does natural selection occur?	1) Living things have variations. 2) They compete for food, shelter, and a mate. 3) Some will have features that help them to survive, and they pass these genes onto their offspring. 4) More of the next generation will have this feature, so will have a better chance of survival and of passing these features onto their offspring.
What are the similarities between natural selection and selective breeding?	- Living organisms have variations. - The most desirable traits survive, and are passed on to offspring. - These offspring have the desirable trait.
What are the differences between natural selection and selective breeding?	- Selective breeding is done by humans. Natural selection is survival of the fittest.
What is evidence for evolution provided by?	Fossil records and from analysis of similarities and differences in the DNA or organisms.
Why is Darwin's theory of evolution a better explanation than Lamarck's?	Darwin's idea accounted for all the observations, for example why simple living things still existed on Earth. It also linked together variation and competition, which hadn't been done before.
How are organisms classified?	Into groups according to similarities and differences in characteristics including physical features and DNA.
How are organisms classified at different levels?	They levels are in an order processing from large groups containing a large number of organisms with a small number of characteristics in common (kingdom) to smaller groups with more characteristics in common (species).
Why is the classification of living organisms useful?	a) It can make sense of the enormous diversity of life on Earth b) It can show the evolutionary relationships between organisms
What is biodiversity?	The variety of life on Earth including: - The number of different species - The range of different types of organism - The genetic variation within species
Why is biodiversity important?	Our food and medicine sources depend upon biodiversity.
What is sustainability?	Meeting the needs of people today without damaging the Earth for future generations.
Why is large-scale monoculture crop production not sustainable?	It doesn't maintain biodiversity.

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