3.2 Component 2 – Biology: Environment, evolution and inheritance
Life on Earth is dependent on photosynthesis to fix carbon dioxide and produce the organic molecules used as the fuels for respiration and life processes.
Living organisms interact with one another and their environment in many different ways. Human behaviours may have beneficial or detrimental effects on natural populations and the environment. The chemicals in the environment are continually cycling through the natural world.
Life on Earth has evolved over time by natural selection, which accounts for biodiversity and how organisms are related. The characteristics of living things depend on both their environment and their genome.
Humans can now use genetic engineering to modify organisms.
What are the feeding relationships between living organisms?
Students should have knowledge and understanding of the followng content.
| Content | Additional guidance and suggested TDAs | Specification reference GCSE Combined Science: Trilogy | Specification reference GCSE Combined Science: Synergy |
|---|---|---|---|
| Outcome 1 | |||
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Radiation from the Sun is the source of energy for living organisms. |
4.4.1.1 |
4.2.2.5 |
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Green plants and algae absorb a small amount of the light that reaches them and make glucose by photosynthesis. These organisms are called producers. Carbon dioxide + water → glucose + oxygen Students should know the word equation for photosynthesis. |
Suggested activity for TDA Investigate the rate of photosynthesis in pond weed. |
4.4.1.1 |
4.2.2.5 |
| Outcome 2 | |||
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Animals and plants may be adapted for survival in the conditions where they normally live. |
Students should be able to explain how organisms are adapted to live in their natural environment given appropriate information in image or prose format. Examples may include polar bears in the Arctic, or cacti in deserts. Suggested activity for TDA Investigate the use of choice chambers, eg with woodlice or maggots. |
4.7.1.4 |
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| Outcome 3 | |||
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Feeding relationships within a community can be represented by a food chain. All food chains begin with a producer. A food web can be used to understand the interdependence of species within an ecosystem in terms of food resources. |
4.7.2.1 |
4.4.2.1 |
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| Outcome 4 | |||
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All materials in the living world are recycled to provide the building blocks for future organisms. |
4.7.2.2 |
4.4.1.2 |
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Decay of dead plants and animals by microorganisms returns carbon to the atmosphere as carbon dioxide to be used by plants in photosynthesis. |
The names of particular microorganisms are not required. Suggested activity for TDA Investigate the change in temperature as grass cuttings decay. |
4.7.2.2 |
4.4.1.2 |
What determines where particular species live?
Students should have knowledge and understanding of the following content.
| Content | Additional guidance and suggested TDAs | Specification reference GCSE Combined Science: Trilogy | Specification reference GCSE Combined Science: Synergy |
|---|---|---|---|
| Outcome 5 | |||
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Plants often compete with each other for light and space, and for water and nutrients from the soil. |
Students will not be required to recall any specific examples of nutrients. Suggested activity for TDA Compare the growth of plants when seeds are planted at different densities. |
4.7.1.1 |
4.4.2.2 |
| Animals often compete with each other for food, mates and territory. |
4.7.1.1 |
4.4.2.2 |
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| Outcome 6 | |||
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Animals and plants are subjected to environmental changes. Such changes may be caused by non-living or living factors. |
An example of a non-living factor is a change in the average temperature or rainfall. An example of a living factor is the introduction of a competitor or predator. Suggested activity for TDA Compare the distribution of plants in a trodden and non- trodden area (using a transect line/quadrat). |
4.7.1.2 and 4.7.1.3 |
4.4.2.3 |
| Outcome 7 | |||
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Pollution of the environment can occur:
Students should recognise that rapid growth in human population means that more resources are used and more waste is produced. |
Suggested activity for TDA Investigate whether rainwater in a city is more acidic than rainwater in the countryside. Suggested activity for TDA Compare the quality of water from different sources eg running water and still water. |
4.7.3.2 |
4.4.2.6 |
How life has developed on Earth
Students should have knowledge and understanding of the following content.
| Content | Additional guidance and suggested TDAs | Specification reference GCSE Combined Science: Trilogy | Specification reference GCSE Combined Science: Synergy |
|---|---|---|---|
| Outcome 8 | |||
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Darwin’s theory of evolution states that all species of living things have evolved from simple life forms that first developed more than three billion years ago. |
Evidence to support this theory of evolution is limited to fossil evidence and the similarity of characteristics between species. |
4.6.2.2 |
4.4.4.2 |
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In natural selection, individuals with characteristics most suited to their environment are most likely to survive to breed successfully. |
An example is the distribution of the peppered moth. |
4.6.2.2 |
4.4.4.2 |
| Artificial selection (selective breeding) is the process by which humans breed plants and animals for particular genetic traits. | Examples include disease resistance in food crops, domestic dogs with a gentle nature and plants with large flowers. |
4.6.2.3 |
4.4.4.5 |
| Outcome 9 | |||
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There are two types of reproduction:
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The term ‘gamete’ is not required. Suggested activity for TDA Asexual reproduction: investigate how alike the plants grown from runners are, eg mint or strawberries. |
4.6.1.1 |
4.4.3.1 |
| Outcome 10 | |||
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The genetic material in the nucleus of a cell is made of a chemical called DNA, which is contained in structures called chromosomes. Students should know that a cell consists of a nucleus that controls the actions of the cell, and cytoplasm. |
4.6.1.3 |
4.4.3.1 |
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Chromosomes carry genes that control the characteristics of the body. Humans have 23 pairs of chromosomes. Only one pair carries the genes that determine sex: females have the same sex chromosomes (XX); in males the chromosomes are different (XY). |
Suggested activity for TDA Investigate whether or not two characteristics are linked, eg finger length and height. Diagrams of genetic crosses will not be required. |
4.6.1.6 |
4.4.3.1 |
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In genetic engineering, genes from chromosomes of humans and other organisms can be ‘cut out’ and transferred to the cells of other organisms. Students should be aware of the potential benefits and risks of genetic engineering. |
4.6.2.4 |
4.4.4.6 |
