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.