Download File - For the love of Science! - with Mrs. Bowers

Evolution:
Change Over Time
Origin of Life
• Abiogenesis (spontaneous generation)
–Life comes from nonliving material
Francesco Redi (1668)
• Disproved spontaneous generation of larger
organisms
– Nonliving material cannot produce life
– Did an experiment involving meat and
maggots
Louis Pasteur (mid-1880’s)
• Disproved spontaneous generation of
microorganisms
– Completely isolated a culture medium with no
outside influence like spores or eggs
• Boiled culture several times
• Observed no living organisms appeared
• Biogenesis: living
organisms come only
from other living
organisms
Scientific theory of the origin of cells
• Scientists believe the first cells probably
prokaryotes (anaerobic): 2 billion years ago
• Unicellular
• Heterotrophs
• Archaebacteria
– Live in harsh environments (deep sea vents
and hot springs)
• Development of photosynthesizing
bacteria
–Released oxygen from water
–Oxygen turned into ozone by sun’s
rays made ozone layer
Endosymbiotic Theory
• Proposed by Lynn Margulis in the 1960’s
• Eukaryotic cells evolved from prokaryotic
cells through a symbiotic relationship
• Chloroplasts and mitochondria contain DNA
similar to DNA in prokaryotes
– Prokaryote ingested aerobic bacteria (produced
energy for the cell)
– Over time the aerobes became mitochondria
– Some prokaryotes also ingested cyanobacteria
(blue/green algae) that contain photosynthetic
pigments
– Cyanobacteria became chloroplasts when
ingested
• Theory of Evolution: proposed by
Charles Darwin
–Observed plant and animal life on the
Galapagos Islands (ex: finches,
tortoises)
–Wrote On the Origin of Species
• Species evolve, not individual organisms
• Occurs by Natural Selection: “Survival of
the Fittest”
– Process by which individuals that are
better adapted to their environment are
more likely to survive and reproduce than
other members of the same species
3 Factors that Affect Natural
Selection
• Overproduction
• Species produce far more offspring
than can survive
• May not be enough resources
(food, water, living space)
• Competition
• Members of a species must compete
with each other to survive
• Does not usually involve direct physical
fighting (usually indirect)
• Lack of finding food
• Predation
• Genetic Variations
– Differences between individuals of
the same species
– Can make individuals better
adapted to their environment (more
likely to survive and reproduce)
– Offspring may inherit helpful
characteristics
– Environmental changes
• Can lead to selection
– Genetic variation
• Can result from the shuffling of
alleles during meiosis or
mutations
• Over time natural selection can lead to change in
populations
– some individuals have differences that permit them to
adapt and increase their chances for survival
– Organisms with favorable variations survive, reproduce,
and pass their variations to the next generation
– Organisms lacking favorable variations less likely to
survive and reproduce
– The ability to survive and reproduce in an environment
is an organism’s fitness.
Evidence for
Evolution
Adaptations
• any variation that aids an organism’s
chances of survival in its environment
– Develop over many generations
– Can be structural or behavioral
Mimicry
Stop at 2:00
• one species can resemble another species
• Can provide protection from predators
• Can look harmful or look like another harmful
species
Camouflage
• Allows species to blend in with their
surroundings
• Used to avoid predators survive to
reproduce
Physiological Adaptations
• Changes in an organism’s metabolic processes
– Bacterial antibiotic resistance
– Resistance to pesticides
• Used to kill harmful insects
• Some insects have traits that protect them from the
pesticide and can survive
• Surviving offspring inherit the pesticide protection
• Pesticide becomes ineffective over several
generations
Fossils
• studied by paleontologists
– Used to learn the history of life
– Evidence of an organism that lived a long time
ago
– 99% of species have become extinct
• Can analyze structures of ancient
organisms
• Can also be used to find out about ancient
climate and geography
Fossil Formation
• Can form in many ways
– Organisms die and become
buried in sediments (particles
of soil and rock, mud, sand, or
clay)
– Become compressed over
time which hardens into rock
• Many found in sedimentary rock
– Oldest fossils in the deepest
layers
– Can show a gradual series of
changes in form of a species
through layers of sediment
Types of Fossils
• Petrified fossils: minerals replace
hard parts of an organism
• Trace fossils: footprints, trials,
burrows
• Molds: decayed organism leaving
an empty space
• Casts: minerals fill spaces
• Preserved remains
• Hard parts: bones, teeth, shells,
leaves
• Imprints
• Amber: resin from trees
• Tar pits
Relative Dating
• Used to determine age of
fossils in layers of rock
• Compares a fossil’s location
relative to other fossils in
nearby rock layers
• Cannot tell actual age
• Look at rock layers oldest
closer to the bottom
The Law of Superposition is that sedimentary rock layer is
older than the layers above it and younger than the layers
below it.
Radiometric Dating
• Used to determine specific age of
rocks and fossils
• Radioactive isotopes in rocks (decay
over time giving off radiation)
• Half-life: decay rate of a radioactive
isotope
Homologous Structures
• Structural features with a common evolutionary
origin
• Similarity in body parts of different organisms due
to a common ancestor
• May differ in function but are similar in structure
• Ex: human hand, bat wing, amphibian leg, bird
wing, whale forelimb
Anatomical evidence
Analogous Structures
• Body parts that do not
have a common
evolutionary origin but are
similar in function and
appearance
• Structures with different
anatomy but similar
function
• Ex: flippers of dolphin,
shark, and penguin, bird
and insect wings
Anatomical evidence
Vestigial Structures
• No current function presently but are similar to
functional structures in related organisms
• No longer serves its original purpose but was
useful to an ancestor
• Still inherited even though it is no longer needed
• Ex: whale pelvic bone, snake leg bone, human
appendix and tail bone
Anatomical evidence
Embryological evidence
• Embryo: earliest stage of
growth and development of
plants and animals
• All embryos have similar
anatomy
• Comparing early
development of different
organisms
• Proceed through similar
stages of development
• Ex: fish, turtles, chickens,
mice, humans all look the
same
• Gill arches and tails
Molecular evidence
(biochemistry)
• DNA Similarities
– Inherited similar genes from a common ancestor
– Compare the sequence of nitrogen bases in DNA of
different species to determine how closely related they
are
– Can compare the order of amino acids in a protein to
compare relatedness
• Cytochrome c – a protein in mitochondria – can
compare the sequence of amino acids to
determine relatedness
Think about it:
1. A human’s appendix and snake legs are
examples of ___.
a. Vestigial organs
b. Fitness
c. Adaptation
d. Struggle for existence
2. Another phrase for natural selection is
“____”.
3. What conditions could force organisms to
compete in a struggle for existence?
Populations and Evolution
• Evolution occurs as a
population’s genes change
over time
– All genes together in a large
gene pool: all of the alleles
in a population’s genes
– Evolution occurs when
there is a change in the
gene pool
• Mutations
–Environmental or by
chance
• Genetic drift: when chance events cause a change
in allele variation
– Ex. Overhunting, natural disasters cause decrease in
population; or isolation of a small group in an area
– Can affect small populations more than large
• Gene flow is the movement of genes from one
population to another population. Examples of this
include a bee carrying pollen from one flower population to
another, or a caribou from one herd mating with members
of another herd.
• 3 different types of natural selection that
acts on variation
– Stabilizing selection
• Favors average individuals in a
population
• Diagram:
• Directional selection
– Favors one of the extreme variations of a
trait
– Diagram:
• Disruptive selection
– Individuals with either extreme of a traits
variation are selected for
– Tends to eliminate the intermediate
phenotypes
– Diagram:
Evolution of Species
• Species: group of organisms that live in the same
area and can interbreed to produce fertile
offspring
• Speciation: the evolution of a new species
– Members of similar populations can no longer
interbreed to produce fertile offspring
– Changes in allele frequencies that can result in the
formation of a new species from a parent species
– Ex: Darwin’s finches
(another speciation video)
• Creation of a new species
– Form when a group of individuals remains
isolated from the rest of its species long enough
to evolve different traits
– Isolation occurs when they are cut off from the
rest of the species
• Geographic Isolation: physical barrier
divides a population
– Bodies of water
– Volcanoes
– Mountain ranges
– Island formation
• Reproductive isolation: organisms can
no longer mate and produce fertile
offspring
–Influenced by different genetic
material and behavior patterns
Patterns of Evolution
• Charles Darwin observed different species
of finches
• Adaptive radiation (aka Divergent Evolution)
– An ancestral species evolves into a variety of
different species to fit a number of different
habitats
• Divergent evolution
– Species that once were similar to an
ancestral species become distinct or
different
– Populations change as they adapt to
new/different environmental conditions
– Results in new species
• Convergent evolution
–Distantly related organisms evolve
similar traits
–Occupy similar environments in
different parts of the world
Ch. 15-17 Bell Ringer #3:
1. The combined genetic information of all
members of a particular population is
called a (an) _____.
2. Genetic drift is more likely to occur in ___.
a. Large populations
b. Medium-sized populations
c. Small populations
d. One individual
3. What is the formation of a new species
called?
Pop Quiz!
1. All living things are ________________.
2. Name 3 types of evidence we can look at to
determine relatedness.
3. What is the significance of the whale leg
bones to evolution?
4. What is currently the closest related
organism to whales?
5. Compare/Contrast whales and their closest
relatives in a paragraph.