Transcript Chapter 15-16

Chapter 15-16
Evolution: Evidence and Theory
Speciation
Evidence for Evolution
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Theories cannot be made without evidence.
One piece or one source of evidence is not enough.
1. Homologous and Analogous Features
2. Vestigial Structures
3. Embryology
4. Macromolecules and DNA
5. Various Fossil Evidence and Transitional Forms
6. Seeing Evolution In Action
7. Coevolution
And much more……
The Fossil Record
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A fossil is a trace of a long- dead organism.
Fossils are often found in layers of sedimentary
rock.
Sedimentary rock is formed when sediment like
dust, sand or mud is deposited and turns to
stone over many years.
A mold is an imprint in rock in the shape of an
organism.
A cast is when a mold fills in with hard minerals.
Sometimes a fossil can form when a whole
animal is preserved in ice or sediment.
What can Fossils Tell Us?
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Law of Superposition states that successive
layers of rock or soil were deposited
The lowest layer is the oldest because it was
deposited first.
Any fossils found in those layers would be
around the same age as the layers.
Relative age is not exact but can only determine
if a fossil is older or younger than another
fossil.
Absolute age is determined using chemical
processes which can show a number of years
for the age of the fossil or rock layer.
Tooth marks on a fossil
Transitional Forms
Extinct
whales
Modern coyote
Whale ear bones-found in no
other living animals
http://www.pbs.org/wgbh/nova/id/program.html
Succession of Forms
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Fossils indicate that species of organisms appeared,
existed for a while and then disappeared or became
extinct.
Mass extinctions occur when large amounts of species
disappear.
Mass extinctions can be caused by the environment like
volcanic activity or from asteroid impacts.
Current extinctions are being caused by humans.
Biogeography is the study of the comparison of fossils
to living organisms.
Biogeography shows that new organisms arise in areas
where similar forms once lived.
Theories of Evolution (Change)
French scientist Jean Baptiste de Lamarck
formed some of the first theories of change by
observing animals with webbed feet and other
animals like giraffes.
 He thought that acquired traits like ones that
are earned through life were passed down to
offspring.
 His idea was easily disproved but Lamarck was
one of the first thinkers of change of his time.
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Remember, Lamarck had the right
idea but the wrong way about it!
You can’t
pass on a
trait that you
have
acquired
through life!
Darwin’s Dangerous Idea
In the mid-1800’s, Charles
Darwin and Alfred Wallace
independently developed an idea
that species were modified by
natural selection.
 In the process of natural
selection, organisms best suited
to their environments
reproduced more successfully
than other organisms.
 Over generations, the favorable
traits increase in the population.
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Voyage of the Beagle
Darwin rode aboard the ship the H.M.S
Beagle as the ship’s naturalist so he could
learn about all the plants and animals he
found.
 Darwin based some of his work on the
research of Charles Lyell who said that
many of the Earth’s geologic processes
took a long time to complete and the
Earth must be quite old.
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Darwin’s Observations
Darwin observed high in the Andes mountains
of South America that fossils of sea creatures
were present. How did they get up there?
 Darwin reasoned that the mountains must have
been uplifted from the sea bed many years ago.
 If the land can change why not the living
creatures there?
 Darwin collected many fossils and observed
thousands of species on his 5 year journey.
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The Galapagos Islands
Darwin visited the Galapagos Islands, an
isolated part of South America.
 There he observed many animals unlike
those found on the mainland of South
America.
 Each island in the Galapagos had unique
animals found no where else. Why?
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Each island has
a different
variation that is
adapted to that
island only and
found no where
else.
Each tortoise is
genetically related to each
other.
Darwin’s Theories
Descent with Modification states that newer
forms appearing in the fossil record are actually
the modified or slightly changed descendents of
older species.
 Modification by Natural Selection states that
the environment may affect individual organisms
in different ways because they are not identical
 Thomas Malthus said populations are limited by
adverse conditions like war, famine and disease
otherwise they would grow unchecked.
 Darwin used Malthus’ ideas in his work.
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Natural Selection
A population of organisms adapt to their
environment as their proportion of genes for
favorable traits increases.
 A single organism’s genetic contribution to the
next generation is termed fitness.
 A favorable trait gives an organism an adaptive
advantage.
 Mutations occur in species which can create
favorable or unfavorable traits in certain
environments.
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Homologous and Analogous
Structures
A homologous structure is a similar
feature that originated in a common
ancestor.
 These structures originate from the same
areas in embryos of the animals.
 Analogous structures are features that
look similar because they are used for a
similar purpose but arise from a different
embryological development like wings in
birds and bees
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Vestigial Structures
Vestigial structures are features that are
no longer useful and have no apparent
function in a current animal but had a
function in a common ancestor.
 Vestigial structures indicate common
lineage.
 Some animals like humans are born with
vestigial structures showing like tails.
 Whales have 4-chambered stomachs like
a cow even though it is not used.
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Wings in flightless and non
aquatic birds
The human
tailbone
Blind fish with remnants of
eyes that are not used
Human wisdom teeth
Sexual parts in
dandelions
They do not use them;
they clone themselves.
Virgin whiptail lizards
clone themselves and no
males are present in the
species.
The lizards still have sex
even though it serves no
purpose.
Males have
nipples and breast
tissue although
they serve no
purpose.
The human appendix is used
in herbivores to digest plant
matter but since humans are
not herbivores, the appendix is
not used.
Embryology
Embryology is the study of embryos and
their development.
 Animals have similar embryos at certain
stages of development indicating a
common ancestor.
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Macromolecules and DNA
All life on this planet has the same DNA
bases and the same types of genes.
 This indicates that we are all related.
 Comparing genes and DNA, comparing
amino acids sequences and comparing
certain protein sequences all lead to the
same conclusion…
 As the number of differences decreases,
the more related the two animals are.
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If you take the
gene for making
an eye in a fruit fly
and put that gene
into a developing
embryo for a
mouse eye, it still
produces a regular
mouse eye.
These are called
homeobox genes
and they control
placement of
appendages in all
bodies of animals.
Evolution in Action
Anyone can see evolution in action every
day.
 Entire populations can evolve into new
species.
 Larger animals take more time while
bacteria and viruses can evolve in a
matter of hours.
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Guppies in high predator
environments lessen
their bright colors for
defense.
Over time the population
becomes lighter and
more drab in color.
Why does this occur?
Brighter colored fish are
eaten more often and do not
pass their genes to the next
generation leaving only the
drab colored fish to
reproduce.
Over time the population
changes or evolves.
Patterns of Evolution
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Coevolution is when two species change together in close
association.
Some species cannot live without the other because they are
so closely connected.
Convergent evolution is when the environment selects
certain features to be similar even though the two animals
may not closely related; sharks and dolphins
Divergent evolution is when two or more related
populations over time become more different. This usually
results in a new species; dogs and wolves.
Divergent evolution is also called adaptive radiation, when
the animals adapt to a specific environment and change into
new species over time.
Artificial selection is when humans select the traits and cause
the evolution; dogs, cats, goldfish, grain crops
Coevolution
The Yucca plant and
Yucca moth, the plant
is only pollinated by
that moth.
Lichens are a mixture
of a fungus and an
algae working
together. They cannot
live without each other.
Coevolution
Many flowers like this
snapdragon are designed
specifically for a certain
insect.
Darwin actually predicted the
existence of a certain moth
by measuring the size of a
flower opening. 40 years
later, the moth was
discovered!
Butterflies have a weak
sense of smell. Flowers
pollinated by butterflies are
usually very fragrant and
have bright colors like red
or orange.
Bees see in UV light and
flowers evolved to
maximize the bees visits by
showing where the nectar
is located. The flower’s
colors glow and the landing
strips show the bee where
to go.
Moths are
nocturnal and do
not need bright
colors to feed.
They need a long
tube like flower.
This flower, the Rafflesia
smells like rotten meat and
poo. Who would pollinate
this plant?
Flowers pollinated by
bats.
Convergent Evolution
Many
marsupials
have placental
counterparts
on other
continents.
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environment
selects an
animal to
occupy a
habitat.
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What is a species?
A species is a group of animals that can
interbreed with each other and produce
offspring that that also breed.
 One species cannot breed with another
and create offspring that can also breed.
 There are many barriers that can restrict
breeding which can contribute to the
formation of a new species.
 Speciation is the formation of a new
species.
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Isolating Mechanisms that cause
Speciation
Geographic isolation is the physical
separation of members of a population.
 Examples are mountains, canyons, island
creation, and separate bodies of water.
 Reproductive isolation creates a barrier
to successful breeding.
 Examples are breeding times, breeding
equipment, sterile offspring, mating calls
and mating behavior
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Many animals have variable
genitalia so proper fit it necessary.
This keeps species separated.