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Transcript
Ch. 8: Survival of Species Vocabulary: species, extinct, fossil, reproduce, endangered species, habitat, pollutant What Is a Species? • A species is a group of organisms that can reproduce with each other and create offspring (babies.) • Animals that are not part of the same species cannot have offspring. • If I were to attempt to mate a cat and a dog, they would not produce kittens or puppies. + ______________ Reproduction • Reproduction occurs when plants or animals make more of their own kind. • Every plant and animal on Earth dies, but a species is considered successful if its members are able to reproduce. • If a species is having trouble reproducing, or reproduces slowly that species is considered endangered. Extinction • In the last chapter we discussed adaptations. • Sometimes an ecosystem will change, because of climate or the introduction or loss of a new plant or animal species. • If the plants and animals in an ecosystem cannot adapt to the new temperatures, plants, or animals they will die out. • If all of a certain type of plant or animal dies, that species becomes extinct. • We know that species have become extinct before, because paleontologists have discovered fossils of plants and animals that don’t exist anymore. Extinction Events • Sometimes the balance of an ecosystem changes. • There are many natural causes for this to happen. • Some of the natural causes are: 1. Climate Change 2. Ecosystem Change 3. Flooding 4. Predators 5. Meteor, Asteroid, or Comet Strike • Sometimes humans can change their environment and cause extinctions. • Some human-made causes are: 1. Overhunting 2. Habitat Destruction 3. Pollution Natural Extinction Events • Climate Change: Where the temperature changes from warm to cold, or from cold to warm • It doesn’t need to change a lot, a few degrees is enough to change the climate of the Earth entirely. Natural Extinction Events • Ecosystem Change: Jungles change into deserts, or forests turn into grasslands. • Natural forest fires, if the plants are not adapted to fire, can cause large tracks of forest to burn down and change the ecosystem from a forest to a grassland for many years. Natural Extinction Events • Flooding: After land gets flooded, if it does not have any place to drain, the plants and animals that used to live there can’t anymore. • In the case of a flash flood, a large amount of water can inundate an area in a matter of minutes. Natural Extinction Events • Predators: When a new species enters an area, it can throw an entire ecosystem out of whack. • Maybe the new animal eats all the prey that the lives in the area; the old predators will die out. • Maybe someone plants a flower that takes over a meadow, choking out all the grasses that used to live there. Natural Extinction Events • Meteor, Asteroid, or Comet Strike: It has been shown that asteroids and meteors strike the Earth very frequently with no ill effects. • When a large enough asteroid, meteor, or comet strikes the Earth, though it can throw up dust and dirt into the atmosphere causing climate change. • Paleontologists think this is what happened to the dinosaurs. Most scientists agree that the Yucatan Peninsula in Mexico was caused by the asteroid strike that killed the dinosaurs. Human-Made Extinction Events • Overhunting: In the past, humans have hunted animals to extinction. • The Tasmanian tiger, the passenger pigeon, and the dodo bird are three examples of species humans have hunted to extinction. • We try not to do this anymore. Human-Made Extinction Events • Habitat Destruction: Humans have not always been careful about the amount of trees that they cut down, or where they build their homes. • When this happens, entire species of plants and animals can be destroyed. Clearcut forest Human-Made Extinction Events • Pollution: We also haven’t always been careful about where we are putting our trash and poisons. • If they are dumped in the wrong stream or area they can cause the extinction of plants and animals. Used oil being dumped into a lake Questions About Chapter 8 1. What happens when a living thing reproduces? 2. What is a habitat? 3. Give three examples of extinct animals. 4. How does extinction work? 5. Write down 2 natural causes of extinction 6. What are 2 human-made causes of extinction?