Evolution and Natural Selection

Change over time

“The Earth is 4,000 years old”

According to some interpretations of the Bible

If Earth was only 4,000 years old…

How could there have been time for all the extinct species, such as dinosaurs to have lived?

“The Earth is very, very old”- Charles Lyell 1797-1875 – Lyell

influenced Charles Darwin’s Theory of Natural Selection

Radiocarbon dating puts the earth at 4.5 Billion years old

Humans have been here less than 1 million years!

Thomas Malthus made a contribution to Darwin’s Theory

Malthus was an economistHe notice that humans produce more offspring than can survive

A group will die every generation

What happens when the population exceeds the resources?

Jean Baptiste Lamarck

1744-1829

Proposed an idea of how organisms change over time

“The Theory of Acquired Characteristics”

Lamark’s theory

Organisms can acquire new traits and pass them on to their offspring

If you lift weights your muscles will be biggerYour children will have stronger arm muscles

Lamarck suggested that giraffes long necks are the result of individual animals

stretching their necks over long periods of time to reach the highest leaves

Charles Darwin

Born in 1809Died in 1882

Published a book called “The Origin of Species”

Suggested a way that species changed over time

The Theory of Natural Selection

1) Variation Exists in all populationsVariation comes from random mutation

2) Those individuals that are best suited to their environment survive and pass on their genes to their young3) Over millions of years species change

“Survival of the Fittest”

Is not accurate

Natural selection is the survival and reproduction of the fittest traits

Adaptation: The changing of a species that results in its being better suited for its environment

Rough Green snakes

Adapted camouflage helps these snakes escape predators

Some species change color in the winter

Rabbits have a coat change in the winter

Turtles adaptation

Turtles haveExceptional nightVision. Unlike us, turtles can see in

color at night

Eagles have extraordinary vision

Vision is 4x as sharp as a humanThey have an extra focal point in the back of their eyeThey can see even when they blink their eye - eyelids are transparent

* can see a rabbit moving a mile away!*

Mollusks also have simple eyes

Mollusks have many eye features that are similar to vertebrates.

LensesRetina

* Their vision is not as good as ours

Flatworm has “eyes”

Not the kind of eye that can see a pictureThey can sense light and dark

Adaptations can be behavioral

Bears hibernate in the winter

Snakes and other reptiles sun themselves on rocks to warm up

Reproductive Adapations

Since Reproduction is necessary for natural selection, species have adapted incredible Reproductive adapations!

Likes and Dislikes of Charles Darwin

Dislikes

Medicine, Blood, Surgery

Likes

Plants and animals esp. animals

Darwin got a job

On the H.M.S. Beagle

His unofficial title was as a naturalist

The Galapagos Islands

Before Darwin left for his voyage, People thought species never changed

But what Darwin found changed that thought

The Galapagos held a vast array of life

Many of the species Darwin found closely resembled species Darwin had seen on the mainland

Darwins drawings of finches

Why would God create so many different finches?

13 islands 13 different finches

They had differences in the size of their beaks

The food they ateSome ate soft nutsSome ate hard-shelled nutsSome ate insectsSome ate berries

Darwin had a Hypothesis

Finches must have arrived at the galapagos a long time ago, and changed after they arrived!

“Descent with Modification”

Tortoises

11 different species of tortoises on the 13 Galapagos Islands

Different size and shell shape

Evidence of Evolution

1) Fossils – found in sedimentary rock, these can be dated and show that many species have changed over time

Evolution of Horse foreleg bones found in fossils

2) Vestigial Structures

Organs or structures in present day animals that are not used anymoreAppendixDid you know whales have leg bones and hips?

They are no longer attached to the spine

This suggests that whales have an ancestor that walked on land!

Evolution of the Whale

3) DNA and Proteins

We all share the same DNA codeMade with the same 4 nucleotidesThe more closely related two species are, the more similarities there are in their DNA code

Humans and chimps are 98% identical!!All mammals have similar proteins

i.e. hemoglobin

DNA evidence

Most species of mammals are over 90% identical in terms of DNA codePseudo genes - multiple copies of DNA sequences that no longer functionHox genes

These are found within gene familiesNot transcribed or translated

4) Comparative Anatomy

Similar Organisms have similar structures – The forearm in Vertebrates all have the same bone structure

5) Artificial Selection

Darwin used this to support his theory, dog breeders select for specific traits in a breed

If humans can change an animals traits, why couldn’t this occur in nature?

Domestic Pigeons? – these were very popular among aristocratic English in the 1800’s!

6) Evolutionary history is seen in the development of Embryos

•Each embryo develops a tail, buds that become limbs and pouches which contain gill - like brachial slits

•Only fish and amphibians retain these and have them develop as gills– Amphibians retain gills in their tadpole

stages but get rid of them when they become adults

7) Microevolution

•Change in small groups has been shown to occur

•Antibiotic resistance is evolution in action!!!

Population Genetics

•Population – A group of genetically similar organisms that live together and interbreed

•Species – A group of organisms that can and do interbreed and produce fertile offspring

Dogs Canis familiaris are all the same species

Horses and Donkeys are not

Isolation

•Two populations of the same species cannot breed with each other

Gradualism

•Change occurs very slowly over very long periods of time

American scientists beg to differ

•Successful species remain unchanged for very long times

•They developed the idea of Punctuated Equilibrium

Michigan State Experiment

•Bacteria reproduce 15,000 times faster than we do

•Grew thousands of generations of bacteria

•Showed that changes in e. coli occurred quickly

•Explains why our fossil histories often lack the “intermediate type”

Species remains unchanged until an environmental stimulus changes

Peppered Moth

•London England

•Use of coal during the Industrial Revolution

Moths had adapted to blend in with the trees they lived on

Use of coal blackened the trees and moths no longer blended in with their surrounding

By the end of the Industrial Revolution, most peppered moths were the darker version

So they adapted to blend in with their surroundings… Aren’t the smart?!

How did they do that?

A mutation occurs randomly, causing the darker versioned moth

Industrial melanism

•The darker version survived better with the blackened trees.

100 years later, trees are back to normal•Which moth will survive better?

New species are formed through Natural Selection•Speciation - appearance of a new

species

•Most evolutionary change is too slow to see

Examples of speciation

•Changes in bacteria

•1969 - a new species of salt bush developed from hybrids of a different salt bush and a salt sage

Salt bush occurs in south Utah

New species of fruit flies have been created using radiation treatment

•Radiation increases the rate of mutation and therefore increases variation

•Why is variation important to evolution?

Speciation is directly linked with the ability to reproduce•As soon as two population become

so genetically different that they cannot produce fertile offspring, they are technically different sepecies

i.e. Domestic Dog and Wolf•The intermediate of a Wolf-dog is

infertile

•In some cases one population will simply out-compete another and extinction of a section will occur

Many times the two species are geographically isolated and they evolve separately

•At one time the Alder flycatcher and the willow fly catcher were considered the same species

Ecological isolation

•Occurs when two species adapt to different habitats.

•When the habitats are different and no crossbreeding occurs,

Sometimes there is a chemical incompatibility between the two gametes•This sometimes occurs in plants

– Sperm and egg may not be chemically compatible

Behavioral Isolation

•Sometimes occurs in animals

•Ex. Leopard Frogs mate at different times in the year and are in the process of becoming different species

•When frogs of one sex in the Northern limit of the range are brought together with frogs in the southern limit, they will not mate

Founder effect

•Occurs when one, or a very few individuals from a population move to a new area. The new population will be genetically different from the first because only the genes of the Founders are available

Genetic Drift

•Change in allele frequency in a population

Bottleneck Effect

•When a stress in the environment occurs and only a few individuals survive, the remaining individuals will determine the genetic makeup of the new population

Hardy Weinberg Equilibrium•We can calculate Allele frequency in a

population with the following formula

• a= dominant allele freqency

• b= recessive allele frequency

• a+b=1

•a2 + 2ab + b2 = 1

•

•a2 = frequency of homozygous Domanant individuals

• b2 = frequency of homozygous Recessive individuals

•2ab = frequency of heterozygous individuals

Hardy Weinberg Equilibrium exits in a population when..

Darwin said in his book, “Origin of Species”, •Humans, gorillas and chimpanzees all

evolved from a common ancestor

•NOTE: WE DID NOT EVOLVE FROM APES!!!

Many fossils strongly confirm this hypothesis

The first primates evolved 50-60 million years ago

They had two features other mammals lacked•1) Grasping hands and feet - young

could hold on to their mothers

•2) Eyes facing forward - many other mammals didn’t see strait out = Better depth perception

Prosimian is an example of a primate that resembles early Primates

•Prosimians survive with their adaptations

•They live in trees

•They use their tails to help them balance

Diurnal v.s Nocturnal

•Diurnal - active during the day

•Nocturnal - active at night

Cone cells developed for daytime seeing•Cone Cells - allow us to see in

color!

Opposable thumbs

•Monkeys feed mainly on fruits and leaves rather than insects and they were the first to have opposable thumbs.

Take away your thumb and see how hard it is to pick up and move objects!

Monkeys appeared in Africa and Asia •Old world Monkeys

New World Monkeys are monkeys in the Americas

Emergence of the apes

•Apes shared a common ancestor with monkeys

Split that occurred with chimps and apes occurred relatively recently

Our ancestors descended along the same lines as the great apes

These are some actual skulls found.