Biology
Exploring differences
We are learning how to: • Identify the differences between different species. • Explain the importance of diversity.
Our knowledge of the diversity of life is greater now than it has been at any other time in the Earth’s history. Some 1.7 million species have been named and classified by scientists. Why do we have such a variety of life? How are species different from each other? Variety of life
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A species is a group of organisms with similar features that distinguish them from all other organisms. Individuals from the same species breed to produce fertile offspring. Scientists estimate that there could be 8.7 million different species on Earth. Although species can be very different from each other, many of them have similar features. The variation between different species is used to classify them into groups. Variation between different species is always greater than the variation within a species. Look at Figure 3.1.2a. These animals all belong to the cat family, but they look very different from each other. 1. What is a species? 2. Look at Figure 3.1.2a. How are the lion, cheetah and tiger similar to each other? How are they different? 3. Which two cats are the same species? How do you know?
Why is biodiversity important?
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Biodiversity is the variety of living things (plants, animals and microorganisms), their relationships and the ecosystems they form. Biodiversity is vital for supporting all life on Earth. It ensures clean air and water, as well as fertile soils. Every organism, no matter how small, has a part to play in what we call the ‘balance of nature’.
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FIGURE 3.1.2a: What are the similarities and differences between small and big cats?
KS3 Science Book 3: Variation for Survival
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