Evolution

Evolution of the Motorcycle

10.2 KEY CONCEPT

Darwin’s voyage provided insight on

evolution.

Darwin observed differences among island species.

1. Variation is a difference in a physical trait.

a. Galápagos tortoises that live in areas w/ tall plants have

long necks and legs; wet areas w/ short plants have

shorter necks

b. Galápagos finches that live in areas w/ hard-shelled nuts

have strong beaks; those that eat fruit have more

delicate beaks.

• An adaptation is a feature that allows an

organism to better survive in its

environment.

– Species are able to adapt to their

environment.

– Adaptations can lead to genetic

change in a population.

• Darwin found fossils of extinct animals that resemble

modern animals (Glyptodon & Armadillo)

• Darwin found fossil shells high up in the Andes mountains.

Darwin observed fossil and geologic evidence

supporting an ancient Earth.

Fossil Evidence included:

• He saw that land

moved from

underwater to above

sea level due to an

earthquake.

• Darwin extended his

observations to the

evolution of

organisms.

Geologic Evidence Included:

10.3 KEY CONCEPT

Darwin proposed natural selection as a

mechanism for evolution.

Several key insights led to Darwin’s idea for natural

selection.

• Darwin noticed a lot of variation in domesticated plants

and animals.

• Artificial selection is a process where humans select traits

through breeding.

neck feathers

crop

tail feathers

Where else do we see artificial selection?

Donkey + Horse =

• Natural selection is a process in which heritable traits

make it more likely for an organism to survive and

successfully reproduce.

• Heritability is the ability of a trait to be passed down.

• There is a struggle for survival due to overpopulation

and limited resources.

• Darwin proposed that adaptations arose over many

generations.

• There are four main principles to the theory of natural

selection.

– Variation: heritable differences that exist in every

population

Natural selection explains how evolution can occur.

• There are four main principles to the theory of natural

selection.

– variation

Natural selection explains how evolution can occur.

– overproduction: having many offspring increases the

chance of survival; results in competition for resources.

• There are four main principles to the theory of natural

selection.

– variation

Natural selection explains how evolution can occur.

– overproduction

– adaptation: a certain variation that allows an individual

to survive better than

other individuals it

competes with.

• There are four main principles to the theory of natural

selection.

– variation

Natural selection explains how evolution can occur.

– overproduction

– adaptation

– descent with modification:

Heritability of adaptations;

as long as the conditions

remain beneficial for the

trait, more individuals will

have the trait in every

following generation.

• Fitness is the

measure of

survival ability and

ability to produce

more offspring.

• Natural selection can act only on traits that already exist.

• Structures take on new functions in addition to their

original function.

Natural selection acts on existing variation.

wrist

bone

five

digits

10.4 KEY CONCEPT

Evidence of common ancestry among

species comes from many sources.

Evidence for evolution in Darwin’s time came from

several sources.

Fossils

• They are preserved remains of organisms that once lived

• They show evidence for evolution because older layers

are more primitive/simpler than those in the upper layers.

• The study of geography provides evidence of evolution.

Geography

– island species most closely resemble nearest mainland

species

– populations can show variation from one island to

another

LE 24-6

A. harrisi A. leucurus

• Embryology provides evidence of evolution.

Larva

Adult barnacle Adult crab

– identical larvae, different adult body forms

– similar embryos, diverse organisms

• The study of anatomy provides evidence of evolution.

Human hand Bat wing Mole foot

– Homologous structures are similar in structure but

different in function.

– Are also evidence of a common ancestor.

• Vestigial structures are remnants of organs or structures that

had a function in an early ancestor.

• Ostrich wings are examples of vestigial structures.

Structural patterns are clues to the history of a species.

Human hand

Bat wing

Mole foot

Fly wing

• The study of anatomy provides evidence of

evolution.

Analogous structures are not evidence of a recent common

ancestor, but they show that the environment plays a role in

putting pressure on organisms to adapt to the same conditions.