Chapter 6: Evolution

Charles Darwin

Georgia Performance Standards

S7CS8 Students will investigate the characteristics of scientific knowledge and how it is achieved.

What is Science?

Science is a way of learning about the natural world…

Science skills – Observing Inferring Predicting Classifying Making models to learn more

Scientific Inquiry/Method

Steps Posing questions Developing a hypothesis Designing an experiment Collecting and interpreting data Drawing conclusions Communicating

Experiments must be repeatable!

Georgia Performance Standards

S7L3 Students will recognize how biological traits are passed on to successive generations.c. Recognize that selective breeding can produce plants or animals with desired traits

This is the study of Genetics…

Georgia Performance Standards

S7L4 Students will examine the dependence of organisms on one another and their environments.

c. Recognize that changes in environmental conditions can affect the survival of both individuals and entire species.

People have always had an impact…

Weather/Climate

Endangered Species

Extinct Animals

Georgia Performance Standards

S7L5 Students will examine the evolution of living organisms through inherited characteristics that promote the survival of successive generations of their offspring.

Most people know nothing about evolution. It is important to know the basic components of the theory.

What is Evolution?

Textbook definition: Evolution

The gradual change in a species over time.

What is a Species?

Textbook definition Species- A group of organisms that are physically similar and can mate with each other and produce offspring that can also mate and reproduce.

What is a variation?

Textbook definition Variation Any difference between individuals of the same species.

What is Natural Selection?

Textbook definition Natural Selection A process by which individuals that are better adapted to their environments are more likely to survive and reproduce than others of the same species.

Before Darwin…

Many scientists believed in the fixation of species – this theory held that all the current animals were the exact same as the first animals…

The problem with this theory was change could be observed and even caused…as in selective breeding.

Selective breeding is artificial selection.

Charles Darwin

British Naturalist that helped shape the theories of evolution.

Darwin developed the idea of Natural Selection: Organisms with the best traits are

more likely to survive and reproduce. These traits will get passed down

from parents to offspring.

Darwin’s Finches

Darwin observed 13 species of finches on the Galapagos Islands.

He noticed they all looked very similar, except for slight differences in body size, beak shape and eating habits.

These are examples of the finches Darwin observed during his time on the island.

Darwin’s Finches (Cont)

Darwin also noticed these finches looked similar to finches along the South American coast.

He hypothesized the 13 Galapagos finches evolved (changed over time) from the South American species.

Competition and Survival

These different groups of birds had to compete for food.

Finches with certain beak shapes, were better able to eat certain foods- These birds survived and reproduced.

After many generations, the different groups of finches became different species.

Variation and Adaptation

Variation- Slight differences in individual traits.

These variations can lead to adaptations over many generations.

Adaptation – a variation that improves the chances for survival.

Example of adaptation - camouflage

Natural Selection

1. Organisms generally produce more offspring than can survive.

2. Differences or variations occur among individuals of a species.

3. These variations are passed to offspring.

Natural Selection

4. Some variations are helpful. Individuals with helpful variations survive and reproduce better than those without these variations.

5. Over time the offspring of individuals with helpful variations may eventually become a separate species.

Peppered Moths Example of natural selection Light colored peppered moths vs. dark

colored moths Pollution from the Industrial

Revolution increased the populations of dark colored moths.

Darker moths suddenly had an advantage over lighter moths.

Natural Selection

Natural selection is sometimes referred to as:

The Survival of the Fittest

Geographic Isolation

Sometimes a small part of a population will get separated from the whole.

Mountains, lakes or oceans can be geographic separators.

Over time, the isolated population can become very different from the original population.

Speed of Evolution and/orNatural selection

Two Theories: Gradualism- Long, slow

process by which one species changes into another species.

Punctuated Equilibrium- Fast form of evolution by which one species suddenly changes into another.

Gradualism…

Clues about evolution

What evidence is available for the theory of evolution?

1. Fossil record in sedimentary rock2. Embryology 3. DNA comparison between species

1. Fossils

Most of the evidence for evolution comes from fossils.

A fossil is the remains, an imprint or a trace of a prehistoric organism.

Most fossils are found in sedimentary rock.

This type of rock is formed when sand, silt, clay and mud are compacted together.

Scientists that study fossils are paleontologists

Fossils

Determining a fossil’s age

Relative dating –younger rock layers are deposited on top.

This estimation is made by comparing the ages of the rock found above and below the fossil in question.

Radiometric dating – this is an age determining process that uses radioactive elements to help determine the age of fossils.

Every radioactive element gives off radiation at a different rate. Half-life = decay of ½ of the atoms of an element.

Scientists can use this rate to help them determine an age of a fossil.

This method does not always produce exact results.

Determining a fossil’s age

Fossil Record

The fossil record is incomplete… Since fossils can’t tell us

everything about evolution other factors are looked at.

2. Embryology

Embryology – the study of embryos and their development.

Structures that resemble a tail, gills or gill slits are found in fish, reptile, bird, and mammal embryos.

These structures suggest a similarity among all vertebrate species.

Homologous structures

These are body parts that are:* similar in structure.* similar in function.

Vestigial structures

These are structures that don’t seem to have any function.

Scientists hypothesize that vestigial structures are body parts that once functioned in an ancestor.

These muscles in horses are larger and allow them to turn their ears toward noise.

3. DNA

Scientist compare DNA of different organisms.

Similar DNA suggests a commonality.

Evolutionists theorize that this indicates that these species had a common ancestor.

Evolution states that these creatures all came from a common ancestor…

Summary

Evolutionists hold that:1. Natural selection occurs:

* only certain individuals in a population are able to survive and reproduce

* the species that exist today look different from their ancestors 2. The fossil record, embryology, and

DNA suggest that all animals have come from a common ancestor.