Transcript The History of Life - Byron Senior High School

Ch. 14 - Evolution
History of Life

The record of life
 Early history of earth
○ High temps, active volcanoes, little free O2
○ Some scientists propose that organisms
formed 3.9 billion years ago
History of Life
 The History of Rocks
○ Fossil – evidence of life found in rocks, 10,000
year minimum
○ Paleontologists – scientists who study ancient
life
 Most fossils are found in what type of rock?
- Sedimentary
 Fossils reveal evidence of environment that existed
when the organisms lived
History of Life

The age of the fossil
 Relative dating – if rock & fossil lay has not
been disturbed, layers @ the surface must
be younger than deeper layers.
History of Life
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Radiometric Dating
 Measures the age of rocks by measuring the
decay of a radioactive isotope
○ Half-life – rate of decay
 C-14 takes 5,730 years for its ½ life
○ Dating technique frequently produces
inconsistent dates because the initial amt. of
isotope can never be known for sure.
History of Life
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Fossils types
 Mold – Depression left (no organism)
 Cast – minerals fill in space – replica of
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organism
Petrified – mineral replace hard parts – fine
detail
Imprints – thin objects leave delicate patterns
Amber/Forzen – actual material in ice or sap
Trace fossils – footprints, wormholes
○ Evidence of an organism
History of Life

Trip through time
 Geologic time scale divided into 4 eras
○ Precambrain – life begins
○ Paleozoic – enormous increase in diversity
○ Mesozoic – changes in organisms
○ Cenozoic – where we are now
 Mass extinction – entire groups of organisms
disappear from fossil record almost at once
Geologic Time Scale
History of Life

Earth began around 4.6 billion years ago
 Life appears ~3.5 billion years ago
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Plate tectonics
 Earth contains several rigid plates that drift
on top of molten rock
History of Life

Origins of life
 Early Ideas
○ Spontaneous Generation – the idea that nonliving material can produce life
History of Life

Francesco Redi – Disproved
spontaneous generation of large
organisms
 Fly's on meat
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Louis Pasteur – disproved
spontaneous generation of small
(micro) organisms
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Biogenesis - Idea that living
organisms come only from other
living organisms
History of life

Origins
 Many theories
○ Can never be proven
 One theory – simple
organic molecules
formed, then become
organized into complex
organic molecules;
nucleic acids, proteins,
and carbs.
○ Tested by Miller & Urey
History of Life

Formation of the Protocell
 Large, ordered structure enclosed by a
membrane that carries out some of life’s
activities (growth and division)
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Evolution of cells
 Proposed characteristics of original cell
○ Anaerobic – No Oxygen needed
○ Heterotrophs – Cannot make their own food
○ Prokaryote – No nuclei
History of Life

Cells
 Eventually used up food supply.
○ Needed to start making their own food
 Photosynthesis (autotrophs)
○ Archeabacteria
 Live in harsh environments
○ Photosynthetic prokaryotes
 Produce O2, which helps produce O3
○ Endosymbiotic Theory
 Eukaryotes evolved from symbiotic relationships
between prokaryotes
History of Life

Endosymbiotic theory
Ch. 15 - Evolution
Natural Selection

Evidence of Evolution
 Charles Darwin and Natural Selection
○ Evolution – Change in a population over time
 Darwin – wrote “Origin of Species” in 1859
 Darwin was a naturalist on the HMS Beagle (1831-
35)
- Collected specimens on the Galapagos Islands
Natural Selection

Natural Selection
 A mechanism for change in a population
○ Organisms with favorable traits survive to
pass on traits
 Organisms produce more offspring that can survive
 Variations exist among all populations
 Variations that are useful in a given environment are
more likely to be passed to the next generation
 Over time, offspring with that “beneficial” variation
make up most of the population
Natural Selection
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Adaptations
 Inherited characteristics which increase the
chances of surviving and reproducing
○ Mimicry
 Structural adaptation to look like another organism
○ Camouflage
 Blending in with the surroundings
○ Physiological adaptations
 Change in metabolic processes
- Bacteria becoming resistant to antibiotics
Natural Selection
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Indirect Evidence of Evolution
 Fossils
○ Provide an early record of early life and possible
relationships to current life on earth
 Anatomy
○ Homologous structures
 Structures that feature with a common evolutionary
origin
- Forelimbs in animals
○ Analogous structures
 Similar function but do not share common ancestors
- Bird and insect wings
Natural Selection
 Vestigial structure
○ Structure of the body that is believe to no longer
have a function – but may have at one time in
history
 Skeletal legs on a snake
 Embryology
○ Study of early stages of development that shows
similarities between fish, reptiles, birds, and
mammals
 Tails and gill slits
 Biochemistry
○ Study of DNA and RNA that shows the
relatedness of species
Mechanisms of Evolution
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Population Genetics and Evolution
 Populations Evolve
○ Not individuals
 Gene Pool
○ All of the different alleles (form of a gene) in a
population
 Allelic frequencies
○ Percentage of any specific allele in the gene pool
 Genetic Equilibrium
○ Frequency of alleles remains the same in a
population over time
Hardy-Weinberg Eq.
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Statement that populations will get to a
point where no diversity occurs.
 Only when the following occurs
○ No mutations
○ No genetic drift
 Alterations in allelic frequencies by chance
○ No gene flow
 Individuals cannot migrate (must stay localized)
Natural selection
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Types of Natural selection
 Stabilizing selection
○ Favors average individuals within a population
 Ex. Baby’s
Natural Selection
 Directional Selection
○ Favors one of the extreme variations of a trait
 Birds beak
 Disruptive Selection
○ Favor either extreme of a trait
 Black and white (no grey)
Evolution of a species
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Speciation
 Evolution of a new species
○ Members of a similar populations no longer
able to interbreed to produce fertile offspring
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Geographic Isolation
 Physical barrier divides a population
○ Volcanic eruption, sea-level change
Evolution of species
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Reproductive isolation
 Formerly interbreeding, organisms can no
longer mate and produce fertile offspring
○ Mating seasons
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Polyploidy
 Species with multiple of the normal set of
chromosomes
○ More common in plants
Evolution of a species
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Rate of speciation
 Gradualism – species originate through a
gradual change of adaptations
 Punctuated Equilibrium – speciation occurs
relatively quickly, in rapid bursts with long
periods of genetic equilibrium in between
Patterns of Evolution
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Adaptive Radiation
 Ancestral species evolves into an array of
species to fit a number of diverse habitats
○ Galapagos finches and Hawaiian honeycreepers
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Divergent Evolution
 One species adapt to different environments
and become different species
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Convergent Evolution
 Distantly related organism evolve similar traits.
Convergent
Evolution
Ch. 16 - Evolution
Primate Adaptations and
Evolution
 What is a primate
 Primate
○ Group of mammals that include lemurs, monkeys,
apes, and humans
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Opposable thumbs – allows grasping
Binocular vision – depth perception
Large brain volume – in comparison to body size
Rotating shoulder and arm flexibility
Varying degrees of grasping ability with feet
Primate Origin
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Division of primates
 Prosimians – small, nocturnal, in tropical forests
○ Lemurs, aye-ayes, tarsiers
 Anthropoids – human like primates with more
complex brains and a more upright posture
○ Monkeys, apes, humans
Primate Origin
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Monkeys – divided into two types
 New world monkeys
○ Found in south central American rainforest
○ Have prehensile tail – for grasping
 Old world monkeys
○ Found in a variety of habitats in Asia and
Africa
○ Do not have a prehensile tail
Human Origin
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Hominids
 Primates that can walk upright on two legs
○ 5-8 million years ago two lines of hominids
diverged from one common ancestor
 Human line
 African ape line (gorilla and chimpanzees)
 Hypothesis based on DNA evidence, there is
little fossil evidence
Human Ancestry
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Advantage of Bipedal
 Speed
 Hands free
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Australopithecine – early
hominid that lived in Africa that
possess ape and human
features
 Nicknamed “LUCY”
 Believed to have walked upright,
but had a small brain
 Estimated to have lived 3.5 mya
Human Ancestry
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Bipedal Fossils
 Foramen Magnum
○ Hole in the base of the skull for spinal cord
 Indicates upright posture
 Broadening of the pelvis allows for stability
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A. afarensis
 Disappears from the record about 1mya
Modern Humans
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Homo habilis – “handy man”
earliest hominid to leave
evidence of stone usage
 Larger brain size
 1.5-2 mya
 Found in Africa by Louis and
Mary Leakey
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Homo erectus-“upright
human” – first to use fire
 Larger brain size
 1.6 mya
 May have hunted
Modern Humans

Homo sapiens – “modern humans”
 100-400 thousand years ago
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Neanderthals – H. sapiens w/ brain size
like “us”
 Lived in Europe, Asia, and Middle East
○ 35-100 thousand years old
○ Thick bones and large faces
○ Believed to have used spoken language and
have religious veiws
Modern Humans
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Cro-Magnon – H. sapien identical to modern humans in
height, skull structure, tooth structure, and brain size
 Tool makers and artists
 Used spoken language
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Exact evolutionary relationships are not known