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Transcript
Evolution and Biodiversity Chapter 4 Core Case Study: Life on Earth • Uniquely suited for life – Temperature range – Liquid water – Gravitational mass – Oxygen • Organisms contribute to relatively consistent planetary conditions – resilient and adaptive • Biodiversity and sustainability 4-1 What Is Biological Evolution and How Does It Occur? • Concept 4-1A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations. • Concept 4-1B Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection). Theory of Evolution • 4.7 billion years • Explains why life so diverse • Supported by fossils, chemical analysis of primitive rock, DNA, and ice cores Population Changes over Time • Populations evolve by becoming genetically different • Genetic variability – mutation Natural Selection • Genetically favorable traits to survive and reproduce • Trait – heritable and lead to differential reproduction • Faced with environmental change – Adapt – Migrate – Become extinct Coevolution • Changes in gene pool of one species lead to changes in gene pool of the other Science Focus: How Did We Become Such a Powerful Species? • Key adaptations – also enabled us to modify environment • Evolved very recently • Technology dominates earth’s life support systems 4-2 How Do Geological and Climate Changes Affect Evolution? • Concept 4-2 Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species. Plate Tectonics • Locations of continents and oceans determine earth’s climate • Movement of continents allow species to move and adapt • Earthquakes and volcanoes affect biological evolution Earth’s Long-term Climate Changes • Cooling and warming periods – affect evolution and extinction of species • Five mass extinctions – Eliminated half of the earth’s species – Many theories why this occurred • Opportunities for the evolution of new species 4-3 What Is an Ecological Niche? • Concept 4-3 As a result of biological evolution, each species plays a specific ecological role called its niche. Unique Roles for Species • Generalist species • Specialist species • Specialists prone to extinction – giant panda Science Focus: Cockroaches • Existed for 350 million years – 3,500 known species • Highly adapted, rapidly producing generalists – Consume almost anything – Endure food shortage – Survive everywhere except polar regions – Avoid predation • Carry human diseases 4-4 How Do Extinction, Speciation, and Human Activities Affect Biodiversity? • Concept 4-4A As environmental conditions change, the balance between formation of new species and extinction of existing ones determines the earth’s biodiversity. • Concept 4-4B Human activities decrease the earth’s biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species. Speciation • Geographic isolation • Reproductive isolation • Millions of years in slow-producing species • Hundreds of years in rapidly reproducing species Extinction • Endemic species vulnerable to extinction • Background extinction • Mass extinction • Balance between speciation and extinction determines biodiversity of earth • Speciation generally more rapid than extinction Human Activities and Extinction • Cause premature extinction of species • Earth took millions of years to recover from previous mass extinctions Humans Change Population Genetics • Artificial selection – slow process • Selective breeding • Crossbreeding – not a form of speciation • Genetic engineering Results of Genetic Engineering • Genetically modified organisms (GMOs) • Gene splitting rapid vs. artificial selection • Modified crops, new drugs, fast-growing animals Pros and Cons of Genetic Engineering • Pros – May help cure genetic defects – May improve organisms – May lead to development of secondary evolution • Cons – Ethical issues – Privacy issues – Designer babies – GMO crossbreeding with original organisms 4-5 How Might Genetic Engineering Affect the Earth’s Life? • Concept 4-5 Genetic engineering enables scientists to transfer genetic traits between different species – a process that holds great promise and raises difficult issues.