B3.1 - How did life on Earth begin and evolve?
- Life on earth began around 3,500 million years ago with small molecules that could copy themselves
- These molecules were produced by the conditions on earth at that time, or from elsewhere
- Evidence for evolution comes from fossils and DNA analysis
- Evolution happens due to natural selection
- Natural Selection: "Survival Of The Fittest"; genetic (mutations) and environmental variation between species means some are better adapted if there is competition, and therefore more likely to survive and breed, passing on genetic variations.
- Selective Breeding: Intentional breeding to produce offspring with desirable features to make money
- Combined effects of mutations, natural selection and environmental changes can produce new species.
B3.3 - Human Evolution & Homeostasis
- The evolution of multicellular organisms has eventually led to nervous and hormonal communication systems
- Receptor cells (ie. eye pupil) detect stimuli (ie. a bright light) and effector cells (ie. iris muscles) produce a response (ie. the pupil becomes smaller)
- In vertebrates, the nervous system is co-ordinated by a Central Nervous System (the brain and spinal cord)
- Nervous System: electrical impulses; fast; short-lived responses.
- Hormones: chemicals; travel via the bloodstream; slow; long-lasting response.
- Some early humans developed a larger brain, giving them a better chance at survival
- Humans and primates evolved from a common ancestor; a species of hominids diverged; all but one of these became extinct (humans)
B3.4 - Extinction
- Living organisms are dependent on the environment and other species for survival
- In the same habitat, different species of animals or plants have to compete for resources
- If one species in a food web becomes extinct, it can have an impact on other species
- Rapid change in the environment can cause a species to become extinct, ie: environmental conditions change; a new predator is introduced; disease.
- Extinction can be caused by direct human activity (ie. hunting) or indirect human activity
- Biodiveristy: The variety of life on earth
- The environment has to be used in a sustainable way so we can preserve it for future use and the development of crops and medicines