B3 – Life On Earth
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Transcript of B3 – Life On Earth
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B3 – Life On Earth
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Food Webs / Competition• Living organisms are dependent on the
environment and other species for their survival• Competition for resources between different
species that are part of the same food web
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Rapid Change may cause Extinction• Environmental Change• New species introduced (competitor,
predator, disease organism)• A species in the food web becomes extinct
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Extinction due to Human Activity• Hunting• Deforestation• Poaching
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• Grey Wolf – 1740 – Great Britain
– Deforestation and hunting• Martinique Amazon Parrot
– 1722 – America – Habitat cleared for
agriculture• Bali Tiger
– 1937 - Indonesia– Habitat loss and hunting
• Caribbean Monk Seal– 1952 – Mexico– Hunted for meat and oil
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Biodiversity• Biodiversity provides high variety of crops,
livestock, forestry, and fish, which are important sources of food and medicine for humans.
• Important for sustainable development
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Evolution• All species that have
ever lived evolved from very simple living things.
• Life on Earth began about 3500 million years ago
• If conditions on Earth at any stage were different, natural selection could have produced different results
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Evidence for Evolution• Fossils• Similarities and Difference in DNA
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The Begining of Life• The first living things
developed from molecules that could copy themselves.
• These molecules were produced by conditions on Earth or have come from elsewhere (asteroid)
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Natural Selection• How evolution happens.• The natural genetic variation within a population of
organisms means that some individuals will survive and reproduce more successfully than others in their current environment.
• This means that more of this organisms genes will be passed on to the next generation
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Environmental and Genetic Variation• Variation is cause by both of these, but only
genetic variation can be passed on to offspring.
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Selective Breeding• Selective breeding is the process of breeding
plants and animals for particular genetic traits.
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Mutations• Mutations are changes in
DNA caused by radiation, viruses or other factors.
• Mutations that occur in sex cells (sperm or egg cells) can be passed onto offspring and may produce new characteristics (eg: 4 wings instead of 2, red eyes, etc)
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Creating a New Species• The combined effects of:
– Environmental Changes– Mutations– Natural Selection
• Can product a new species over time
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Evolution of Multi-cellular Organisms• Led to nervous and hormonal communication
systems
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Receptor and Effector Cells
• Neurones (Nerve Cells) link receptor cells to effector cells
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Central Nervous System• In vertebrates, the nervous system is
coordinated by the CNS
• The Nervous System uses electrical impulses for fast, short-lived responses. It doesn’t make permanent, long lasting changes
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Hormones• Chemicals which travel in the blood and bring
about slower, longer-lasting responses.
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Examples
• Nervous Communication– Blinking– Muscle Control– Heart Beat
• Hormonal Communication– Puberty (Testosterone, Oestrogen)– Mood, appetite, sleep (Serotonin)– Increase heart rate and blood pressure (Dopamine)
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Homeostasis• Nervous and Hormonal systems are involved in
maintaining a constant internal environment
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Larger Brain• Evolution of larger
brain gave early humans a better chance of survival– Smarter– Quicker– More social– More artistic– Language
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Human Evolution
• Common Ancestor
• Divergence (Separation) of Hominid Species
• Extinction of all but one of these species