Transcript Evolution Review

Evolution Review
What this unit focused on!
Here Today, Gone Tomorrow?
 Key concepts
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Making decisions about complex issues often
involves trade-offs
Many life forms have gone extinct in the past.
Extinction can be related to environmental
changes.
Extinct species often have living relatives, i.e.
closely related species that live on after them.
Here Today, Gone Tomorrow?
 Extinct mammoths are more
closely related to Asian
Elephants than African
Elephants.
 Could we?
 Should we?
 Re-create the mammoth?
Fossils
 Fossils:
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Help us determine features & behaviors
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major source of evidence used to determine
relationships among species
Used to develop theory of evolution
Come from bones, nails, teeth, etc.
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 Earth is about 4.5 billion years old and life forms have
existed on it for over 3.5 billion years.
Geological Time Line
 Know the geological timeline – know which major developments
happened where
 Bacteria
 Protozoa
 Age of Fishes
 Age of Reptiles
 Age of Dinosaurs
 Age of Mammals
 The Great Extinction
 The Second Great Extinction
 Pangaea
 Flowering Plants
 Bees
 Horses
 Humans
Geologic Time Scale
 Earth = 4.6 bya
 Oldest evidence of life = 3.5 bya
 The divisions of the geologic time scale
are determined by the first or last
appearance of certain fossils in the fossil
record.
 Several mass extinctions have occurred =
CATASTROPHISM
Geologic Time Scale
 The time scale does not divide the history of
Earth into blocks of equal duration. The
boundaries between sections are defined by
the first or last appearance of certain fossils in
the fossil record.
Reading the Rocks
 Law of Superposition
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Older rocks are at the BOTTOM
Younger rocks are at the TOP
A Meeting of the Minds
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Many life forms have gone extinct in the past.
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Extinction can be related to environmental changes.
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Variations occur naturally within populations, and
provides the raw material for natural selection.
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Only inheritable traits are transmitted by reproduction
and thus can change over generations due to natural
selection.
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Competition for survival and reproduction determines
which genetic traits are more likely to be transmitted to
future generations.
A Meeting of the Minds
Darwin
Lamarck
Jean-Baptiste Lamarck’s theory
 Inheritance of acquired characteristics
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Frequent and vigorous use of a body part led
to a slight increase in its size.
These changes were heritable and could lead
to an entire population to transform gradually
over time.
Charles Darwin’s Theory
 Adaptations occur over many generations by
a population.
 MAIN CONTRIBUTION: variation exists
within any population and leads to natural
selection
Charles Darwin and Alfred Wallace
 Known as “Natural Selection”
 1. Variation within a species occurs naturally
 2. Organisms must compete for limited
resources to survive.
 3. The individuals that are better suited for
the current environmental conditions survive
and reproduce more often than the others do
 4. As a result, the genes and traits that are
most common in a population can change
through time.
Which stars are best suited for the
environment?
Which stars are best suited for the
environment?
Battling Beaks
 Competition for survival and reproduction
determines which genetic traits are more
likely to be transmitted to future generations.
 Under different environmental conditions,
natural selection acts upon the same species
differently.
 Genes Mutate. Individuals are selected.
Populations evolve.
Battling Beaks
 Random mutations during DNA replication
continually introduce new variation into all
populations.
Origins of Species
 Mutations can be advantageous, disadvantageous,
or neutral
 Under different environmental conditions, natural
selection acts upon the same species differently,
favoring different variants; this can lead to
speciation.
Origins of Species
 Darwin found:
 Each species has a particular role within its ecosystem.
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Variation occur & get passed onto new generations.
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Mutations cause variation.
Darwin and the Galapagos Islands
Family Histories
 Single-celled organisms
 Multi-celled invertebrates
 Fish
 Amphibians
 Reptiles
 Birds
 Mammals
Family Histories
Family Histories
 Fish appeared first in the early Paleozoic Era
 Reptiles appeared next in the late Paleozoic
Era
 Mammals appeared in the Mesozoic Era but
many more mammals appeared during the
Cenozoic Era.
A Whale of a Tale
 Use skeletons & fossils to trace changes in anatomy
over time
 Natural selection explains changes (adaptations)
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Modern whales evolved from small land dwelling
mammals
Whales!
A Whale of a Tale
 Land creatures evolved into sea creatures
 The stepwise shift in habitat from land to shallow water to open
ocean involved many adaptations, which occurred in large part
over the 20 million years between about 55 and 35 million years
ago.
 Shift of nostrils
 Streamlining the body shape
 Reduction and elimination of hind legs
 Transforming the forelimbs into flippers
 Strengthening of the tail
 Addition of tail flukes
 Modification of ears and eyes
 Loss of most hair
 Acquisition of a layer of insulating blubber