LS CH 6: Change Over Time
Name:
Review: Hypothesis, Theory, Law

Hypothesiso _
about what should happen in an investigation


“
.”
Lawo A statement that


in nature
“
.”
Theoryo An
for natural phenomena

“
.”
o Based on:

_
testing or observations and
confirmed hypotheses
o _
_

A scientific theory (

Definition: The
)
o Restated: The changes in

in closely related organisms over time.
_
of any theory in biology.
o “Nothing in biology makes sense except in the light of evolution.” –Theodosius Dobhansky (Russian
Biologist).

Supposed for hundreds of years, but lacked a mechanism
o That is, a method for why it occurs
Early Idea About Evolution

Jean-Baptiste
(1744-1829)
o Hypothesis:
o Believed that
o This is closer than anyone before him, but
_

1800’s British Scientist

Wrote several books
o _
(1859)

_
o Chart coastlines of South America
o Darwin collected specimens of plants and animals
Development of Darwin’s Theory

_
, his grandfather, believed that
time, but didn’t know how
o Darwin learned this reading his grandfather’s writings

Darwin also read Lemarck’s works, but thought it unlikely
o A lot of people criticized Lemarck’s idea

Around this time, a lot of fossils were being discovered
o _

___ was making tons of discoveries, including that the earth was much older than was thought
Maybe the most influential to Darwin was
, an economist
o Malthus was one of the first to realize that


_

The maximum number of organisms that can be supported by the environment

Draw his graph here:
Artificial Selection
o Also called
o _

Cows with more milk, strong horses, friendly wolves, many more
o Over time, offspring will have desired trait
Darwin’s Journey

H.M.S. Beagle
o Collected plant and animals from different regions

_
Islands
o Learned that

Also similar, yet different, to those in South America
o The
o Darwin’s
Darwin’s Principles

Based on what he had learned, and what he had seen on his journey, Darwin came up with 4 basic principles
o 1.
o 2.

Different traits (recall, Darwin did not know about genes or DNA)

_
o 3.
o 4.
Natural Selection

Darwin’s great insight into the natural world

The process by which organisms with variations that help them survive in their environment have a better
chance to survive long enough to reproduce, passing the traits on.
o Restated:
…

_
Variation and Adaptation

_
are the _
within a species
o Height, color, speed, etc.
o _____________ variations are _________; ____________ variations are

.
_
o Beneficial variations
o Increase the chance for survival and reproducing

Keeps the species alive
o These are what natural selection acts on

Types of Adaptations
o _
Adaptations:

Involve

o _
, such as color, size, shape, anatomy, etc.
Examples: Camouflage, speed, strength, better teeth for meat eating, etc.
Adaptations:

Involve how an organism

Nocturnal hunters limit competition and are able to attack while prey sleep
o _
Adaptations:

Involve

, biochemical changes
Hibernation, photosynthesis, etc.
o Examples of Adaptations

_
- Being able to

_
- Looking like another species

with surroundings
One that is venomous, poisonous, or tastes bad
Importance of Darwin’s Theory

Darwin did not invent the idea of evolution
o He came up with the

It was already accepted that species change over time
o Nobody knew how

Darwin answered the question

Nature (environmental conditions) determine which traits will survive and which will
not

In the 150 years since Darwin published his Theory, it has been one of the most tested and studied theories in
science
o It has continually passed
Predictions From Darwin’s Theory

A
to explain how traits are passed
o _
came up with this around the same time Darwin was completing his Theory,
unaware of Darwin’s ideas

Mendel actually tried communicating his idea to Darwin, but it never reached him
o _
from changing
environmental conditions

Happens all of the time

Confirmed by DNA studies
o _
Speciation

The _
o A species is a

Evolution occurs in
(members of a single species in an area)

If a population is
(split from initial population) they may
evolve to the point where they are no longer able to reproduce with members of their original species
o At this point, a new species has been born

This is
Evolution vs. Extinction

Species have 2 possible outcomes:
or
o Extinction is the

It is final… for now

When environmental conditions change, species must

There have been several
, or will go
(death of >50% of Earth’s species in a
geologically short period of time)
o We are currently part of another one driven by changing environmental conditions

Which we are causing…
Biological evidence For Evolution

Often takes a long time, so often relies on
o Though it

, many times, even recently
Evidence includes:
o Fossils

_

Location of the fossil tells us about organism
o Deeper in rock layers=older
o Can tell us about cause of death
o Sometimes found with food or eggs

Even if incomplete, good clue to past

Many different types

_
o Can be an imprint, a cast or mold, an organism preserved in amber
o Comparative anatomy

Similarities between organisms

_
-similar structures found in different organisms
which are not closely related
o _
Structures

Structures an organism has that

May still do something, but not what it used to do

Examples:

_
-Used by some organisms to digest large amounts of
cellulose (plant materials)
o In humans, it holds some bacteria, but is not necessary to our survival


Can actually kill us…
_
- Makes fur-covered organisms look bigger (cats)
o No purpose in humans

_
- Were useful for ancestors that relied on coarse, rough foods
o Now only cause problems
o Actually disappearing from human population

35% of people born will never have Wisdom Teeth

Many others will only get 1 or 2
o Embryology

Study of
o DNA Evidence

All organisms have

All use the same 4 bases (A,T,G,C)

Similar genes for cellular jobs

Sequence of nucleotides shows strong similarities
o Follows “

” pattern of visible features
_
o Predictable mutations to DNA show speciation events