Transcript Evolution- What`s That?

Evolution
Sections 15-1 & 15-2
Life’s Diversity

On Earth there are millions of different
types of organisms
=
biodiversity
What is a Theory?

In science, the word theory takes on a new
and very different meaning.
A scientific theory is…
•
Testable
•
Well-supported
•
Based on facts, observations, and
hypotheses
Evolution

Why is there so much biodiversity?
 evolution

= change over time
Process of by which modern organisms have
descended from ancient organisms
Lamarck

First person to propose a theory of evolution.
 Law of use and disuse
 An organism can lose or change a body
feature during its life time and passes it on to
their children
Using it -improves
2. Not using it - disappear
1.
•short-neck giraffes stretched their necks to reach higher
into trees for food = acquired longer necks
•this acquired characteristic was passed on to (inherited
by) their off-spring
Charles Darwin

Disproved Lamarck’s
theory of evolution

Darwin’s new
theory was based
on …
natural selection
Not a chance,
Lamarck!
Charles Darwin

sailed on the Beagle around the world.
Voyage of the Beagle

made observations, collected fossils, living
organisms, and studied the Earth

Some fossils looked like living organisms
while others looked foreign
The Importance of Fossils

Darwin asked important questions as he
collected the fossils.
Why had so
many species
disappeared?
Are these
fossilized species
related to living
species?
What other
important info
do fossils hold?
The Galapagos Islands
Islands were close together but had very
different climates
 Darwin studied the animals on the islands
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Darwin

evolution affects populations


environmental changes cause evolution


Same as Lamarck
organisms with certain features are
naturally selected


Not just individual
hummingbirds with slightly longer beaks are naturally selected for
certain organisms survive

hummingbirds with the longer beaks will survive.
Darwin explained evolution by
NATURAL
SELECTION
Mutations

A change in the DNA code, that forms a
new trait
Can be good = increase survival
 Can be bad = decrease survival

Darwin’s Findings

Adaptation
A
beneficial trait (good mutation) that helps an
organism survive and reproduce

Adaptations evolve (develop or change over
time) (1000’s years)
 Anatomical
- Teeth, body covering
 Physiological - movement, camouflage, mimicry
Adaptation?



My partially webbed
hind feet help me to
swim.
My flattened tail acts
as a rudder.
My teeth help me to
shred cattails and
other plants to build
my lodge.
Sea otter
Adaptation?



My hard outer shell
helps to protect my
soft body from
predators.
I can make my own
cement to attach
myself to stationary
objects.
I have feathery legs
for trapping plankton
and other food.
Barnacles
Adaptation?



My long beak helps
me to drink the nectar
from plants.
My wings help me to
hover in one place.
My small body is
lightweight.
Hummingbird
Behavior adaptations
can be learned or instinctive.
Social behavior - some animals live by themselves,
while other live in groups.
Behavior for protection - can help to protect the

1.
2.
animal. For instance the opossum plays dead. A rabbit
freezes when it thinks it has been seen.
•
•
Migration (birds, whales)
Hibernation (bats, snakes, bears)
Artificial Selection
 Aka
selective breeding
humans
choose attractive mates
cattle ranchers choose biggest and
healthiest cows
Farmers choose biggest tomatoes
Natural Selection
Nature selects the best traits
 best traits survive
 Survive and reproduce = fitness
 “survival of the fittest”

4 points of Natural Selection

"survival of the fittest"
1.
Variations exist among members of a
population
Many more individuals are produced than will
survive
Members of a population compete for food,
space, mates...
Individuals that are better adapted survive &
reproduce
2.
3.
4.
Stop talking, Goodnight.
Evidence of Evolution
1.
2.
3.
4.
5.
Fossils
Bio-geographical
Anatomical
Embryological
Biochemical
1. Fossils
2. Biogeographical

Geographic Distribution of Living Species
? why similar species lived in
different locations?
3. Anatomical

Homologous Body Structures
• (definition) different mature
forms, but develop from the
same embryonic tissues.
• means they all had a
common ancestor.
4. Embryology
In the early stages of
development, the embryos
of many different species
look very similar.
 Means = a common
ancestor!

5. Biochemical

same basic biochemical molecules
 DNA,

ATP, enzymes ...
Similarities in amino acid sequences
(DNA codes) means = a common ancestor