Evolution

Explanations of Evolution

Chapter 29

1853~ wrote book about his studies on evolution and his theory of Natural Selection.

1. Living things overproduce:

More offspring are produced than survive.

Above: Cottonwood tree produces over a 1,000 seeds

Left: Frog eggs!!!

2. There is variation among the offspring.

Variation: trait that makes an individual different from others of its species

Where is the variation among the Tiger Moths???

Wing pattern!

3. There is a struggle to survive.

More living things than there are resources to go around.

Competition: the struggle among living things to get their needs for life.

4. Natural selection is always taking place.

~less desirable trait are less fit.

~reproduce fewer offspring

~desirable traits are more fit

~reproduce more offspring

~organisms today are better suited for their surroundings.

Darwin knew that species within an organism are always changing!

~Takes time!!

Evolution: is a change in the hereditary features of a group of organisms over time.

Try this…

Can you think of how evolution has changed using NONbiological examples??

FOSSILS~ are the remains of once living things from ages past

Life forms that is no longer exists.

What animal is this?

What living animal is it similar to?

Sedimentary Rock: forms from layers of mud, sand, and other fine particles

Animals/Plants die, settle to bottom of waters.

Sediment change into rock over time & form fossils.

Fossil give scientist records of what was living at different times. Gives scientist an idea of the history of life on Earth!

Newest layer of rock, younger layer of fossils.

Older layer of rocks is located at the bottom-first layer that was formed!

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Embryo’s of different organisms look alike. How is the similar appearance of embryos evidence of evolution?

All animals are chordates… They have a common ancestry. Share some of the same traits, results in all embryos looking similar.

Early life forms~ made of DNA

Later life forms~ made of DNA

Vestigial structures is a body part that no longer has a function.

Appendix~

Used in rabbits to aid in digestion of plant materials.

Changes in fossils

Similarities in embryos

Gene code

Vestigial structures

Review…

1. List and describe the 4 major points of Darwin’s theory of natural selection.

2. Give several examples of fossils and tell where they are formed.

3. Describe how the embryo’s are alike.

4. An athlete breaks her leg in HS. She has a son who walks with a limp. Is this an example of Evolution?

Adaptation: trait that makes a living thing able to survive in its surroundings.

Example of SurvivalCan you see the mouse?

Owls cannot see mice that are dark in color and that are on a dark surface. What would happen if this was a white mouse?

Dark mice will survive, reproduce, continue to outnumber white mice.

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– The owl!

Mutations

• Change in the DNA code

• Could this be helpful or harmful to the organisms?

Remember what adaptations are…help living things survive…controlled by genes

Mutations may supply living things with new source of traits/adaptations.

Mutations continued

• Mutation are natural events.

• Appear in every living thing.

• Change in genes may be helpful, harmful, or have no effect at all!!

Species: is a group of living things that can breed with others of the same species and form fertile offspring.

Fertile: being able to reproduce by forming egg and sperm cells.

Macaws~ look alike but belong to different species.

A new Problem…Shallow stream with bunnies on both sides. A flood occurs. Bunnies live apart for thousands of years.

Living conditions on either side of the stream are different. Individual lacking traits favorable for the new environment have died. Favorable traits have survived and reproduced. Groups gradually become different b/c environments are different. Each group may become a different species.

Charles Darwin studied finches (bird).

Numerous species of finches. Each has a different beak shape.

Small beaks~ eat insects

Thick beaks~ eats seeds

How did the finches come to live on the island?