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Biological Diversity What is it? • The wealth of species that live on the Earth • This includes individual species, habitat, genetic varieties, or the number or abundance of species Biological Evolution • This is the change in inherited characteristics of a population from generation to generation What causes Evolution? 1. Competition for resources 2. Ability to adapt to environmental conditions • As the environment changes, so to do the species that live there Unifying Principles of Evolution • Perpetual Change: All species are in a continuous state of change How does Evolution Occur? 1. Natural Selection • The process of increasing the proportion of better adapted offspring • Mutations create variations which may lead to better adapted individuals better suited for the environment • These organisms then reproduce, passing along these better genes Darwinian Natural Selection • Three conditions necessary for evolution by natural selection to occur: – Natural variability for a trait in a population – Trait must be heritable – Trait must lead to differential reproduction • A heritable trait that enables organisms to survive AND reproduce is called an adaptation How Does Evolution Occur? 2. Migration (Gene Flow) • The movement of organisms (and genetic makeup) from area to another • Can become geographically isolated leading to divergent evolution. This is when two organism, isolated from one another for long periods of time, become genetically different Example of Migration Emu vs. Ostrich vs. Rhea Australia Africa South America When faced with a change in environmental condition, a population of a species can get MAD: – MIGRATE to a more favorable location – ALREADY be adapted – DIE • Natural selection can only act on inherited alleles already present in the population—do not think that the environment creates favorable heritable characteristics! • Soooo….how do new alleles arise?????? MUTATIONS, MY FRIENDS! • Changes in the structure of the DNA • Adds genetic diversity to the population • May or may not be adaptive – Depends on the environment! How Does Evolution Occur? 3. Mutation • This is when an organisms DNA is altered somehow. • This changes the organisms genotype or genetic makeup • Mutations can be advantageous, disadvantageous, or neutral 4. Genetic Drift • These are changes in population due to chance • Chance does not take sides and does not necessarily help the better adapted to survive Island Ecology • Islands have fewer species on them • Smaller islands and island farther away have even fewer • Example – Galapagos Islands • Darwin observed many different finch populations on the island and concluded they all came from a single species • This was know as Adaptive radiation. Each finch has a specialized role • The finches different beaks are specialized for different food sources • Problem is that small populations can be easily wiped out by storms, floods, disease, climate change or predators • Most island contain smaller sized animals. This is due to the fact that resources are limited. Being small requires less energy to survive • Homo floresiensis – dwarf humans found on the island Flores in Indonesia • 3-4 feet tall • May have become extinct due to volcanic eruptions • Ecological Island – small amount of habitat cut off from other large segments of habitat • Example – Rock Cut State Park Number of Species • Thought to be between 3-10 million, but truly not known • Why? New species are discovered and go extinct all the time • Insects – 500,000 species • Plants – 230,000 species • Mammals – 4500 species Why are there so many species? • Each has different ecological niches 1. More complex the habit, the more biodiversity 2. Topography increases biodiversity Ex. Hills, mountains, hotter and wetter climates 3. Wildfires can increase biodiversity 4. People affect biodiversity -Urbanization decreases biodiversity Threatened and Endangered Some numbers that are in danger of extinction: • 23% of mammalian species • 12% of birds • 4% of reptiles • 31% of amphibians • 3% of plants • Endangered species – a species that is on the verge of becoming extinct • Threatened species any species that is likely to become endangered • Local extinction – when a species disappears from part of its range but can be found elsewhere • Global extinction – when a species can no longer be found anywhere on the planet Why save them? 1. A symbol of wilderness 2. So that habitats can manage themselves and we can observe natural habitats 3. Save genetic variation in the wilderness 4. Save genetic material for future use 5. Also don’t forget about the four justifications (Moral, Aesthetic, Utilitarian, Ecological Extinctions • Throughout Earths history there have been mass extinctions • Some species exist for hundreds of million years, other for just a few million • Six major mass extinctions have occurred in the past 550 my. Hey Dinosaurs, what happened? • 65 mya • Evidence suggest that an asteroid hit the earth • This impact caused food chains to break down and many animals could not adapt. More recent extinctions • 20-10,000 years ago • Extinction of large mammals and birds • Smaller mammals and animals tended to survive, population the world today as we know it. Are Humans at Fault? Yes. How? 1.Hunting or harvesting -Commercial purposes, sport, destroyed because they are a pest Ex- Ivory from elephants, rhino horns 2. Disrupting, fragmenting, or eliminating habitats Ex- Farming 3. Introducing exotic species Ex- African honey bees led to the development of killer bees 4. Pollution Ex- industrial chemicals and pesticides Species who’s status has improved Elephant seal- dwindled to about a few thousand animals around 1900 because of over hunting. Presently in the hundreds of thousands. • Sea otter – hunted for fur reducing its numbers to several hundred but today numbering around 10,000 • Blue Whale – reduced to around 400 due to whaling. Numbers are increasing but slowly. • Bald eagle, Osprey, Peregrine falcon – all decimated because of the use of the pesticide DDT. • The Endangered Species Act of 1973 has saved many of these animals Is abundance a problem? • Yes. Increased confrontations with humans. • Sea lion populations have increased so much their excrement can pollute waterways • Mountain lion populations can affect the safety of an area with increased attacks.