29-1 Changes in Living Things• Objectives:• 1. Give examples of how adaptations help organisms survive• 2. Explain how changes in life-form occur• 3. Describe the classification and evolution of primates and humans
Adaptation• An adaptation is a trait that allows living things to survive in it’s surroundings• Examples: – Color – Long legs – Webbed feet – Claws
Natural Selection• Natural Selection is the process in which something in a living things surroundings determines if it will or will not survive to have offspring• Something in nature does the selecting• Living things that are suited to their surrounding will survive and pass their traits on to their offspring.• If they are not suited, then thy will not reproduce and there will be no offspring
Mutations• A mutation is a change in the DNA code.• Since traits are controlled by genes, then adaptations are controlled by genes• Not all mutations are helpful and help with survival
• Mutations are natural events and may be helpful, harmful or have no effect at all. They can occur in all living things• Examples: – A deer born with a white coat no longer blends in with its surroundings. It can be seen more easily by its enemies and may be eaten. It does not pass its new trait on to its offspring – A deer is born with longer legs which allows it to run faster and get away from its enemies. It is not eaten and can pass on this trait to its offspring so more deer with longer legs are born
Species Formation• A species is a group of living things that can breed with with others of the same species and form fertile offspring• Fertile means able to reproduce by forming an egg or sperm cells• Only members of the same species can breed and form offspring
• If a natural barrier, such as a wide river, was created, animals on either side could not swim cross and breed with each other.• Over time the two groups would gradually become different because their environments are different• In time, each group becomes a new species
• Charles Darwin discovered this on his exploration of the Galapagos Islands.• He discovered several species of Finches with different types of beaks• Each Finch lived on an island and did not breed with the birds on another island• Over time each Finch species developed a different beak adapted to eating the specific seeds found on the island because they did not come in contact with each other
Events that can lead to thedevelopment of a new species1. A barrier is formed that separates members of a species, such as a flood, mountains, glacier or lava flow2. The animals found them selves living in different environments3. Groups began to show different traits because of natural selection4. Over time the two groups became different and if brought back together again they would not be able to breed and have fertile offspring
Primates and Human Evolution• The classification of humans is:• Phylum: Chordate - Class: Mammal - Order: Primate Primates include monkeys, apes and humans• Primates are mammals with eyes that face forward, a well developed cerebrum and thumbs that can be used for grasping• Humanlike ancestors first appeared around 3 million years ago.
• These ancestors walk upright, but were much shorter than modern humans.• Several different humanlike species evolved, but they became extinct• Two groups of homo sapiens lived on earth. One was called Neanderthal, but it became extinct• The other developed into modern humans of today
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