F. DARWIN’S EVIDENCE

FOR EVOLUTION

1. Fossils - fit a pattern

2. Homologous structures similar structures doing very different functions

a. bones in adults

Tiktaalik was discovered in 2006

b. structures in embryos

fish salamander turtle chicken pig mouse dog human

fish salamander turtle chicken pig mouse dog human

fish salamander turtle chicken pig mouse dog human

3. vestigial features [pg 525]

structures with no function in one organism but have a function in similar organisms

eg human appendix,

The appendix of the gorilla is massive, accounting for its ‘fat’ stomach.

This appendix houses bacteria that breakdown cellulose

whale pelvis

A whale pelvis has the same bones as land animals, but is not attached to the spine and so is useless.

4. artificial selection a. dogs

All of these dogs have a recent common ancestor.

b. pigeons

Darwin kept pigeons and was familiar with their breeding and how almost any trait could be selected for by the breeder..

the key is that artificial selection happens much faster

as humans discard the unsuitable breeders

5. Mechanisms of Darwinian Evolution by Natural Selection

ASSUMPTIONS

1. offspring vary

Note the differences among these kittens.

2. some of this variation is heritable

Setters produce setter pups, not retriever pups.

3. more offspring are born than can survive

If all of these baby spiders survived, the world would be overrun!

4. populations generally do not increase in size

INFERENCES

1. individuals of the same species will compete

2. the survivors will pass on their ‘favourable’ traits to the next generation

3. over time, there will be more traits from the survivors in the population

6. Macroevolution vs Microevolution

Macroevolution – change to form new species

eg Darwin’s finches

many species arising from one common ancestor

this takes a very long time

[10,000’s millions of years]

Microevolution - change within a species

eg. bacteria antibiotic resistance

all were sprayed with herbicide but one remains green

this takes only a short time [10’s 1000’s of years]

and weeds herbicide resistance

Prior to industrialization, the light form was most common

In this one species, there are two forms of moths

eg. peppered moths

light-coloured pre-Industrial trees

light-coloured pre-Industrial trees

dark-coloured post-Industrial trees

prior to industrialization, the light form was most common

after industrialization, the dark form became the most common

Studies showed that predators selected the easier to find moths

Darwin’s explanation for the longer necks in giraffes?

He knew that some baby giraffe’s are born with slightly longer necks.

There is limited food and so these longer-necked giraffes might get more food and do better.

Over time, more of the population would consist of loner necked giraffes.

But Darwin was wrong!!

Neck length is giraffes has nothing to do with food

Giraffes spend most of their time eating low, not high

And bending down to get a drink is very awkward

So why do giraffes need long necks?

For fighting!!

EVIDENCE OF EVOLUTION # 1-7

time to work on these questions now