Transcript many generations pass…

Evolution
The process of
accumulating small
changes in a species
over time that eventually
results in a new species.
?
1-2
These birds are all members of
the same species. What variations
can you see among them?
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
What are resources for these birds?
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…
1st
environmental
change
6
The environment changes. A disease kills
off all the bushes with red flowers.
What trait might be an adaptation in the new environment?
7
Why were RED birds selected against?
…many generations pass…
X
…many generations pass…
• 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
X
…many generations pass…
…many generations pass…
2nd
environmental
change
8
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?
…many generations pass…
…many generations pass…
…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…
3rd
environmental
change
9
A disease kills the berry bushes. Now the
only food available is small rodents.
What other trait might be an adaptation in this new environment?
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…
4th
environmental
change
10-11
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?
Common pigeon
(what variations do you see?)
Harris hawk
-are often hunted by predators
-good hunters
- eyes on side of head are good
for looking all around for danger
- eyes on front of head are good
for seeing/targeting far off prey
…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…
Mutations
are random!
Some birds are born with a
purple & yellow feather mutation.
Is this trait an adaptation? Is it likely to be passed down to offspring?
X
…many generations pass…
5th
change
12-14
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?
…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…
6th
environmental
change
15 & 16
Some birds are born with a plumage
mutation. Birds with this mutation
attract more mates.
Is this trait an adaptation?
Can it be passed down to offspring?
…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…
7th
environmental
change
17 & 18
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?
…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. FALSE
b) The mutation for short tails was most likely caused by the tail lice FALSE
c) Organisms can only pass on mutations that they are born with. TRUE
d) Species with few variations have a better chance of dealing with changes in the
environment. FALSE
e) Mutations can be good or bad or neutral. TRUE
f) Whether a mutation is good or bad depends on the environment. TRUE
g) In nature, many variations may exist long before they are useful. TRUE
h) Natural Selection means organisms choose their traits & choose whether they live
or die. FALSE
i) Natural Selection over many, many generations leads to evolution. TRUE
21. What does the arrow in the diagram at bottom
right represent?
Evolution by Natural Selection
50,000 years
ago
old species
today
new species