Evidence of Species Change

Evidence of Evolution

What is evolution? Evolution is change over time Scientific theory of evolution explains how living

things descended from earlier organisms

Evidence of Evolution

What evidence supports evolution? Fossils

Fossils are preserved remains or traces of organisms that lived in the past

Scientists can infer the structure of ancient organisms by looking at fossils

Fossil evidence supports the idea that living things evolved from earlier organisms

Evidence of Evolution

Evidence of Evolution What evidence supports evolution?

Similarities in DNA and protein Scientists infer that species inherited many of the same genes

from a common ancestor Genes are segments of DNA that determine the

characteristics in an organism The more similar the sequence of bases in a strand of DNA,

the more closely the organisms are related Genes determine the types of protein produced Proteins are made of amino acids Scientists compare sequences of amino acids to determine

closeness Evidence from DNA and protein structures has confirmed

conclusions based on fossils, embryos, and body structure

Section of Cytochrome c Protein in AnimalsThe table shows the sequence of amino acids in one region of a protein, cytochrome c, for five different animals. Each letter corresponds to a different amino acid in the protein.

Evidence of Evolution

Evidence of Evolution

What evidence supports evolution? Similarities in body structure

An organism’s body structure is its basic body plan Similar structures that related species have inherited

from a common ancestor are called homologous structures

Homologous StructuresThe bones in a bird’s wing, a dolphin’s flipper, and a dog’s leg have similar structures. Which bones in the dog's leg match those in the flipper and which match those in the wing?

Evidence of Evolution

Evidence of Evolution

What evidence supports evolution? Similarities in early development

Scientists infer evolutionary relationships by comparing the early development of different organisms

Evidence of Evolution

Can you tell which of these four embryos is:

a. pigb. chickenc. turtled. fish

Evidence of Evolution

Similarities in DevelopmentThese four organisms all look similar during their early development. What are similarities and differences among them?

Evidence of Evolution - Classwork

1. Compare and contrast the bones of a bird’s wing and a seal’s flipper.

2. What can scientists infer from the similarities between these two structures?

3. Describe how DNA evidence might be used to confirm scientists’ conclusions about any relationship between birds and seals

Darwin’s Theory

What was Darwin’s hypothesis?In 1831, the HMS Beagle set sail from England on a

five year trip around the worldNaturalist Charles Darwin was on board. He Was amazed by the diversity of living organisms

(different from England) Saw fossils of animals (that resembled the bones

of then-living organisms) that had died long ago Compared species living on the Galapagos

Islands with those living on the mainland of South America

Darwin’s Theory

What was Darwin’s hypothesis? Compared species living on different Galapagos

Islands Concluded that different finches he found on the

Galapagos Islands were descended from the same finches he found on the mainland of South America

Different finches developed different beak shapes and sizes depending on the food they ate

Darwin’s Theory

What was Darwin’s hypothesis? Beak shape is an example of an adaptation, a

trait that increases an organism’s ability to survive and reproduce

Darwin’s hypothesis was that species change over many generations and become better adapted to new conditions

This hypothesis had become known as the Scientific Theory of Evolution, because it is a well-supported and widely accepted explanation

Galápagos FinchesThe structure of each bird’s beak is an adaptation to the type of food the bird eats. Match each finch to the type of food you think it eats.

Darwin’s Theory

Darwin’s Theory

What was Darwin’s hypothesis?Update Peter Raymond Grant and Barbara Rosemary

Grant,  British evolutionary biologists have spent six months of the year each year since 1973 capturing, tagging, and taking blood samples of the finches on the island.

They have demonstrated how very rapid changes in body and beak size in response to changes in the food supply are driven by natural selection. 

Darwin’s Theory

What was Darwin’s hypothesis? Darwin studied domestic animals produced by

artificial selection (selective breeding) In artificial selection, only organisms with

desired traits are bred A trait is a specific characteristic that an organism

can pass to its offspring

Ideas about Evolution

What was Darwin’s hypothesis? Species

Individuals of the same species can interbreed and have fertile offspring

Individuals of the same genus, but not the same species, may be able to interbreed, but their offspring are not fertile

Ideas about Evolution

What was Darwin’s hypothesis? Artificial selection

All dogs and wolves are Canis lupus Wolves are Canis lupus lupus Domestic dogs are Canis lupus familiaris Since they are all the same species, wolves and dogs

they can interbreed and have fertile offspring

The wolf

Great Dane

Chihuahua

Breeds of domestic dogs

Darwin’s Theory - Classwork

How does artificial selection support Darwin’s hypothesis?