B3 Life on Earth

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Define a species.
A species is a group of organisms that can breed together to produce fertile offspring.
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How can animals and plants survive in many different environments and what does this mean?
They can adapt to different environments which increases the species' chance of survival by making it more likely that individuals will reproduce.
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How is the cactus well adapted for hot, dry (desert) conditions?
1) rounded shape, small surface area compared to volume- reduce water loss 2)thick waxy cuticle and leaves reduced to spines to reduce water loss 3) shallow but deep roots, large absorption of water
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How are fish adapted to aquatic environments?
1)Gills which extract oxygen from water for respiration 2) tail fins with a large surface area to propel them though water 3)streamlined bodies to decrease water resistance.
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Why do individuals of the same species have differences?
These differences are called variation, and some is genetic which occurs when genes change- mutations.
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Describe the process of natural selection.
'Survival of the fittest'- Living things show genetic variation. When there is a change in the environment, some characteristics make individuals more likely to survive and reproduce and therefore spreading on this advantageous feature.
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Discuss competition and interdependence within a food chain.
The environment provides resources essential for life and therefore they are competed for. Organisms also depend on organisms- interdependence.
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How could a change in the environment cause the extinction of species?
1)Environment changes beyond species ability to adapt 2)A new competitor, disease or predator is introduced 3)A species in the food web becomes extinct.
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What do plants use the energy they obtain from the Sun for?
Plants absorb a small percentage of the Sun's energy for photosynthesis. This energy is stored in the chemicals which make up the plant's cells.
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Give examples of energy transferred between organisms in an ecosystem.
When animals eat plants/animals and when decay organisms (decomposers and detritivores) feed on dead organisms and waste material.
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How is energy lost at each trophic level of a food chain?
Respiration, heat energy (mammals and birds need a constant temperature), waste products (droppings/urine) and uneaten parts of organisms (bones).
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What is the equation to calculate the efficiency of energy transfer?
energy avaliable to the next stage / energy that was avaliable to the previous stage X 100
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Describe the carbon cycle, the different processes.
Photosynthesis in plants removes Carbon Dioxide from the air, it is turned into sugars. Eating of the plant passes the carbon onto animals. Both animals and plants respire releasing carbon dioxide. Plants and animals die and decompose..
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Describe the carbon cycle, the different processes (2).
..and are broken down by microorganisms which release C02 by respiration as they break down the material. After millions of years, carbon compounds from dead organisms fossilise and when burnt, release c02.
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Why does atmospheric nitrogen need to be converted into nitrates?
Nitrogen gas is very unreactive and cannot be used directly be plants and animals. Nitrogen is needed for making proteins for growth and needs to be turned into nitrates.
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How does atmospheric nitrogen get converted into nitrates?
1) Nitrogen-fixing bacteria which live in soil and inside root nodules (swellings) or leguminous plants. This can also happen with lightning, at such a high energy it reacts the oxygen and nitrogen. (Nitrogen fixation)
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Explain the role of nitrifying bacteria.
Plant and animal remains and waste contains ammonia. Nitrifying bacteria turns ammonia in decaying bacteria into nitrates. (Nitrification)
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How do nitrates leave the soil?
1) Denitrifying bacteria- turn nitrates back into nitrogen (denitrification) or 2)Nitrates are absorbed by the roots of plants which then get eaten.
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What important roles do microorganisms play within the nitrogen cycle?
Decomposition, nitrogen fixation and denitrification.
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Name 3 non-living indicators that can be used to measure environmental change.
1)Temperature- could indicate the climate is changing e.g global warming. 2)Nitrate level- measures changes to water. An increase in nitrate level could be caused by sewage or fertilisers contaminating a supply. 3)C02- increase, fossil fuels, globalw
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Name 2 other living indicators that can be used to measure environmental change.
1)Lichen- monitors air pollution, sensitive to sulfur dioxide. The number and type of lichen indicates how clean the air is. 2)Phytoplankton-populations increase when nitrate and phosphate levels increase which indicates water pollution.
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How do mayfly nymphs, which are aquatic river organisms, indicate environmental change?
They are sensitive to levels of oxygen in water. If you find mayfly nymphs in a river, it indicated that the water is clean.
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How long ago did life on Earth begin and how did it start?
3500 million years ag, life evolved from very simple organisms
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What is the difference between natural selection and selective breeding?
Natural selection only chooses features which help survival, selective breeding may not.
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What are two pieces of evidence for evolution?
1)Fossil record, species getting more and more advanced as time goes on. 2)All living things share some DNA which indicates they all evolved from simple life forms.
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How did Darwin come to his conclusion that evolution was the result of natural selection?
Many observations of organisms and applying creative thinking to his findings.
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How do scientists classify organisms?
By the similarties in their characteristics (genetics, DNA) and their physical features (e.g vertebrates have a backbone).
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What does classification show us? Why is it useful?
Shows the evolutionary relationships between different organisms.
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What is biodiversity?
The number of different species on Earth, the range of different types of organisms (E.g plants and animals) and the genetic variation between organisms of the same species.
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Why is maintaining biodiversity important?
The more plants we have, the more resources there are for developing new food crops and medicines.
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What is sustainability and how can we be sustainable?
Sustainability means meeting the needs of today's population without harming the environment for future generations. Maintaining biodiversity is a big part in this.
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Why is large-scale monoculture crop production not sustainable?
This is when farmers grow fields containing only one type of crop, it does not maintain biodiversity as it supports fewer types of species than several crops.
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How do you increase the sustainability of using packaging materials?
1)Renewable materials so you are not using up finite resources 2) Less energy- use recycled materials not to damage the environment 3)Less pollution-biodegradable materials so they decompose
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Why is decreasing the use of packaging material the most sustainable option?
Even biodegradable materials take a while to breakdown because there is not much oxygen avaliable. Also, making and transporting any packaging material uses up energy.
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Card 2

Front

How can animals and plants survive in many different environments and what does this mean?

Back

They can adapt to different environments which increases the species' chance of survival by making it more likely that individuals will reproduce.

Card 3

Front

How is the cactus well adapted for hot, dry (desert) conditions?

Back

Preview of the front of card 3

Card 4

Front

How are fish adapted to aquatic environments?

Back

Preview of the front of card 4

Card 5

Front

Why do individuals of the same species have differences?

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