The Unifying Theme of Biology Evolution The Unifying Theme of Biology

True or False? Evolution says that man came from monkeys. Scientists do not agree on the theory of evolution. There is much evidence to support the idea of evolution by natural selection. Charles Darwin was the first scientist to describe the idea of evolution. Evolution is the idea that the organisms on Earth today have descended from ancestors and gradually changed during that process.

What is Evolution? A process by which modern organisms have descended from ancient organisms Change in the frequency of certain genes in a population over time

What is the Evidence For Evolution? The Fossil Record Evidence from Living Organisms

What is the Fossil Record? A collection of fossils that represents the preserved collective history of Earth’s organisms

Examples of Fossils Whole preserved animals or plants Skeletons or fragments of bone Footprints Eggs

Do all Living Things form Fossils? NO Fossil formation requires specific conditions which are not common Extremely cold temperatures Hot, dry climate Quantities of sap Sedimentary rock This means that the Fossil Record is incomplete like a puzzle with pieces missing

What Does the Fossil Record Tell Us? The Earth is very old and changed slowly over time by natural forces like: Weathering Floods Volcanoes Shifting land

There have been major changes in Earth’s climate and geography over time Fossils of tropical plants have been found in Antarctica Fossils of shark teeth have been found in Arizona

Species have become extinct

Species alive today are similar to those that lived in the past

Questions Define the word “evolve”. List two general areas that have provided evidence for evolution. Fossils are only bones? Explain why this statement is true or false. Why have scientists been unable to find all the fossils they need to demonstrate the evolution of organisms? Have the species alive today always existed? Explain.

What is the Evidence from Living Organisms that Supports Evolution? Similarities is Embryo Development Similarities in Body Structures Similarities in Chemical Compounds

How are Embryos Similar? Due to a shared genetic blueprint (DNA) Hox cluster-in vertebrates it controls the pattern of organ and structures from head to tail (differences are due to helpful mutations)

What are Some Similarities in Body Structures Among Organisms? Homologous Structures- develop from the same body parts but meet different needs (homo=same)

Vestigial Organs- structures that are no longer needed and may decrease in size Snakes-tiny remnants of leg bones Humans-appendix

Which Chemicals are Shared Among Organisms? Nucleic Acids DNA RNA ATP

Questions How do the embryos of vertebrates compare at the earliest stages of development? How does the presence of homologous structures support the theory of evolution? Name some chemicals that all living things share.

How Does Evolution Occur? “Nothing in Biology makes sense except in the light of evolution.” Theodor Dobzhansky biologist

What were Some Early Explanations for Evolutionary Change? Jean Baptiste de Lamarck (1744-1829) Desire to change- living things have an inborn urge to become more fit for their environment Use and Disuse- organisms can alter their shape by using their bodies in new ways Passing on Acquired Traits- characteristics obtained during a lifetime are passed on to offspring

What is the Current Theory of Evolutionary Change? Charles Darwin Evolution by Natural Selection

Living Things Overproduce More offspring are created that can survive

Offspring Vary in their Traits No two offspring are exactly alike due to gametes having different sets of genes mutations

There is a Struggle for Existence Against each other Mates Food Shelter Habitat

Survival of the Fittest The best adapted offspring survive and pass their genes (traits) on to their offspring

Questions How did the artificial selection carried out by farmers help Darwin develop his theory of natural selection? What are the four points of Darwin’s Theory of Natural Selection. Compare the ideas of Darwin and Lamarck regarding evolution. Were Lamarck’s ideas truly scientific? Why or why not? What did Darwin mean by “fitness”?

How Do New Species Develop? Isolation-members of a population are separated and can no longer interbreed Natural Selection will work differently on each group because they are now in different environments Different adaptations may develop and the gene pools will differ

What are Some Processes of Genetic Change? Natural Selection Adaptive Radiation Convergent Evolution

Natural Selection The genes (and the traits they control) that are best suited will be passed on and those that are not suited will die out

Adaptive Radiation A number of different species form from a common ancestor Radiate-move away from the center Adapt-evolve traits best suited for the new environment

Convergent Evolution Different species evolve features with similar functions but different origins and structures (analogous structures) Wings-butterfly vs bird Eye-dog vs fly

Questions Why is the concept of isolation important for natural selection? Explain how new species are formed by adaptive radiation. What are analogous organs? Give some examples. What type of evolution results in the formation of analogous organs?