Transcript Evolution powerpoint

Life on Earth: The
Theory of Evolution
What is a Theory
 Video Segment 1
 https://www.youtube.com/watch?v=85di
EXbJBIk&list=PL5270149AB732F0FB&i
ndex=1
Origin of Life
 Before the 17th century people believed
in a process called spontaneous
generation.
 Living things could arise from non-living
things.
 Why did they think that?
 If they would leave rotting meat out then
maggot seem to appear so the meat must
give rise to maggots. (NOT Exactly)
Experiments
 In 1668, Redi proved spontaneous generation
to be false
 Meat and Flies
 Spallanzani also preformed an experiment
 2 broth flasks (boiled)
 Problem: what happens to bacteria when you
cook them?
 1800’s, Louis Pasteur modified Spallanzani’s
experiment
 Used curved necked flask
Earth’s History
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Earth is about 4.6 billion years old
No usable oxygen.
Anaerobic organisms.
The fossil evidence says they were most
likely prokaryotes
 Probably heterotrophs
 Some may have also been autotrophs
 Archaebacteria bacteria that uses chemosynthesis
instead of photosynthesis
We need More Oxygen
 Some relatives to cyanobacteria used
photosynthesis  more oxygen is
formed.
 Some of this oxygen went into the upper
atmosphere where it formed the ozone
layer.
 The ozone layer helps protect the earth
from ultraviolet radiation that can damage
DNA
More complex cells form
 So we have prokaryotes that are
aerobic and are not to complex
 Endosymbiosis
 The small invaders would give rise to
mitochondria and chloroplasts
 Mitochondria and chloroplast have their own
circular DNA that is different from the cells DNA
Possible
explanations for
the things that
have been
observed.
???
Lamarck’s explanation
 His hypothesis
 Similar species descended from a common
ancestor
 His evidence
 Fossil records
 His reasoning
 Acquired trait are passed on to offspring
 Things passed on due to experience not
genetic
“The Inheritance of
Acquired
Characteristics”
 Example:
A giraffe acquired its long neck because its
ancestor stretched higher and higher into the
trees to reach leaves, and that the animal’s
increasingly lengthened neck was passed on
to its offspring.
Darwin and Wallace
 About 50 years later, two scientists,
Charles Darwin and Alfred Wallace,
both came up with the same idea:
natural selection
 Natural selection: organisms that are
best suited for their environment are
able to reproduce hence passing on the
favorable traits.
Charles Darwin
 Darwin set sail on the H.M.S. Beagle (18311836) to survey the south seas (mainly
South America and the Galapagos Islands)
to collect plants and animals.
 On the Galapagos Islands, Darwin observed
species that lived no where else in the world.
 These observations led Darwin to write a
book.
 Video Segment 2 “Who is Charles Darwin”
 https://www.youtube.com/watch?v=vmphlb
RhLu8&list=PL5270149AB732F0FB&index
=2
Darwin’s Two Theories
 Descent with modification
 Newer forms appearing in the fossil record are
really modified descendants of older species
 Modification by natural selection
 Describes how evolution occurs
 Environment affects populations, some organisms
can cope and others cannot.
 Adapting results in a change in the genetic make-up of
the population (selective advantage)
 Fitness is a single organisms contribution to change
Natural Selection
 Individuals with favorable traits are
more likely to leave more offspring
better suited for their environment.
 Example:
English peppered moth (Biston
betularia)
- light and dark phases
Natural Selection
1. All species produce offspring at a
faster rate than food supplies can
increase.
2. Except for identical twins, no two
individuals are exactly alike.
3. In each generation, more individuals
are produced than can survive.
4. Individuals that possess certain traits
have an advantage over those that do
not.
Natural Selection
5. Geographical isolation may lead to the
formation of a new species.
6. The environment determines whether
a trait is beneficial.
7. Traits are inherited and passed on to
the next generation.
8. Over time, successful variations
accumulate in a population, and a new
species may appear.
https://www.youtube.com/watch?v=ewtw_nZUIDQ&list=PL52701
49AB732F0FB&index=3
Darwin’s key idea: Natural Selection
**Four tenants of natural selection**
1. Genetic Variation: Variety of traits exist. These variations are
called alleles. Example: blue eyes, brown eyes.
2. Overproduction of offspring: Organisms produce more
offspring than can survive
3. Struggle for existence (Survival of the fittest): Organisms
compete over resources to survive and reproduce.
Organisms best suit for environment survive to pass on
genes.
4. Differential survival & reproduction: over time, traits of
successful reproducers become more common
Evidence of Evolution
Biogeography – Plate Tectonics
Fossil Record
Adaptations
Comparative Anatomy
1.
2.
3.
4.
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Vestigial Structures
Homologous/Analogous structures
5. Comparative embryology
6. Molecular biology
How does it work
 Video Segment #4: How Does
Evolution Really Work?
 https://www.youtube.com/watch?v=xkw
RTIKXaxg&index=4&list=PL5270149AB
732F0FB
Biogeography
Geographical
distribution of species.
Organisms tend to
arise in areas where
similar organisms
lived in the past
Comparative Anatomy:
Structural similarities link
related species
Vestigial Structures
 Features that are not used by the organism
but may have been useful to ancestors
 Example:
 In humans: tailbone, appendix
 In whales: pelvic bone and four chambered
stomach
 In snakes: pelvic bone, limb bones
Homologous
structures
Homologous: structures that are similar because of
common ancestry and develop similarly
Homologous and embryo
 Complete the homologous and embryo
color sheet following the teacher
directions.
Comparative
embryology
Study of
structures that
appear during
embryonic
development.
Molecular biology
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DNA and proteins (amino acids)
Mutations are changes in the DNA.
Gene flow is any movement of genes from
one population to another.
Sexual Reproduction
Convergent Evolution
 Species from different evolutionary branches
may come to resemble each other even
though they are not closely related
 Example:
1. Ostrich (Africa) & Emus (Australia).
2. Sidewinder (Mojave Desert) &
Horned Viper (Middle East Desert)
3. Sharks and Dolphins
Divergent Evolution
 2 or more species or related population
become more and more dissimilar
 Can result in a new species
 Types:
 Adaptive radiation: related species evolve
from a single ancestral species (Galapagos
finches)
 Artificial selection: breeding organisms for
specific trait (dogs)
Writing
 Under your notes
 Write me a paragraph in detail describing
what you have learned so far about
evolution.
 We have done dot lab, checks lab, evidence
of evolution, theory of evolution, lamark
versus Darwin.
Mechanisms of Change
1. Mutation
 A change in the DNA sequence.
(1 in 100,000) leads to new traits.
Some traits will be advantageous to the
species.
2. Migration
 Movement of individuals form
one population into another.
 Can alter the genetic
characteristics of a population.
Mechanisms of Change
3. Nonrandom Mating- controls the genes

When individuals mate with one another more or
less frequently: example inbreeding.
4. Selection
 Artificial Selection –
individuals breed
organisms for specific
traits.
 Natural Selection environment dictates
Which traits are needed
to survive.
Mechanisms of Change
5. Genetic Drift
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Random loss of alleles. Small population
a person does not reproduce.
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Founder effect – one or a few individuals
migrate and become an isolated population
with distinct genotypes.
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The population splits due to migration events
Bottle neck – restrictions in genetic variability
due to flooding or natural disasters.
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The population splits due to natural disasters
Speciation
(How do we get a new species?)
 Usually involves successive change
 Local populations of a species become isolated
and more specialized (adapted)
 Natural selection acts to keep them specialized
(different from the larger population)
 Populations of a species must become
reproductively isolated in order to develop
into new species.
Mechanisms of Change
 Complete the coloring sheet Gene Flow
 Be sure to read and highlight
 Color neatly
 Complete the coloring sheet Genetic
Drift
 Be sure to read and highlight
 Color neatly