evolution the process of accumulating small changes in a species over time that eventually results...

EvolutionThe process of accumulating small changes in a species over time that eventually results in a new species.

?

These birds are all members ofthe same species. What variationscan you see among them?

1-2

What are resources for these birds?

The Birds’ Environment: lots of bushes and trees, (some with red flowers), lots of berries & small rodents available, lots of streams, some predators that eat these birds

3-4

Resource: things in the environment that are necessary for survival of a species. (food, water, shelter, air, a mate)

…many generations pass…

…many more generations pass…

…and more generations pass…

…many, many, many generations pass…

The environment changes. A disease kills off all the bushes with red flowers.

What trait might be an adaptation in the new environment?6

Why were RED birds selected against?

7

1st environmental

change

…many generations pass…

X

…many generations pass…

X

• Birds with red feathers got eaten easily. (no camouflage)• Birds with red feathers had few or no offspring.• Birds with brown feathers survived, had lots of offspring

…many generations pass…

…many generations pass…

Too many birds, not enough berries. But there are lots of small rodents to eat, too.

What body feature might be good for catching rodents?8

2nd environmental

change

…many generations pass…

X

…many generations pass…

X

…many generations pass…

• Birds with bigger talons got more resources. • Birds with small talons got fewer resources.• Birds with small talons died or had few offspring.

X

…many generations pass…

…many generations pass…

A disease kills the berry bushes. Now theonly food available is small rodents.

What other trait might be an adaptation in this new environment?9

3rd environmental

change

side view of beaks

…many generations pass…

X

…many generations pass…

• Birds with stronger beaks got more resources. • Birds with skinny beaks got fewer resources.• Birds with skinny beaks had few or no offspring.

X

…many generations pass…

…many generations pass…

A new predator (a species of hawk) shows up and grows in population,

by eating these birds.

What 2 traits might be adaptations in the new environment?(what variations do you see?)

10-11

4th environmental

change

- are often hunted by predators- eyes on side of head are good

for looking all around for danger

- good hunters- eyes on front of head are good

for seeing/targeting far off prey

Common pigeon Harris hawk

…many generations pass…

X

…many generations pass…

…many generations pass…

• Birds with longer wings could fly faster. • Birds with eyes on the side of the head could see approaching danger from all directions better.• Birds with shorter wings and front-eyes got caught and

eaten more often (and had fewer offspring)

X

…many generations pass…

…many generations pass…

Some birds are born with apurple & yellow feather mutation.

Is this trait an adaptation? Is it likely to be passed down to offspring?

X

Mutations are random!

…many generations pass…

Some birds are born with a green feather mutation. The color matches the leaves.

Is this trait an adaptation? Can it be passed down to offspring?12-14

5th

change

…many generations pass…

X

…many generations pass…

• Birds with green feathers have great camouflage. • Birds with brown feathers are easier for predators to see.• Birds with brown feathers are more likely to be prey and

so will have fewer offspring (they die young).

X

…many generations pass…

…many generations pass…

Some birds are born with a plumagemutation. Birds with this mutation

attract more mates.

Is this trait an adaptation? Can it be passed down to offspring?

15 & 16

6th environmental

change

…many generations pass…

…many generations pass…

• Birds with head plumage get more mates. • Birds with no head plumage get few mates.• Birds with head plumage have more offspring.

X

…many generations pass…

Tail lice are a parasite that carry disease and cause feather loss. Tail lice thrive in hot weather. Now the climate heats up, causing many more tail lice infestations.

What birds will have more tail lice? Fewer tail lice?

7th environmental

change

17 & 18

…many generations pass…

X

…many generations pass…

…many generations pass…

• Birds with short tails have fewer tail-lice (more healthy)• Birds with big tails have more tail lice (not healthy)• Healthy birds get mates and have lots of offspring.

X

…many generations pass…

Let’s compare…

50,000 years ago Today

(beak side view)

(beak side view)

Evolution

The process of accumulating many small changes in a species over time that eventually results in a new species.

a) If an organism needs a useful trait, it can get that trait during its lifetime.

b) The mutation for short tails was most likely caused by the tail lice

c) Organisms can only pass on mutations that they are born with. d) Species with few variations have a better chance of dealing with changes in the

environment.

e) Mutations can be good or bad or neutral. f) Whether a mutation is good or bad depends on the environment.

g) In nature, many variations may exist long before they are useful.

h) Natural Selection means organisms choose their traits & choose whether they live or die.

i) Natural Selection over many, many generations leads to evolution.

TRUE

FALSE

FALSE

FALSE

TRUE

TRUE

TRUE

FALSE

TRUE

21. What does the arrow in the diagram at bottom right represent?

today50,000 years ago

old species new species

Evolution by Natural Selection