Transcript Adaptations over time

Adaptations over
time
Charles Darwin
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1800’s British Naturalist
 Very interested in the natural
world
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Went on a voyage with a
crew who was studying the
South American coast
 Ship called H.M.S. Beagle
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Took many notes and
species throughout the
journey
 Especially interested in the
species of birds that he found on
a group of islands called the
Galapagos.
Galapagos Islands
Birds on the Galapagos Islands
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Darwin is most known for the birds that he found.
 He captured several birds and sent them back to England to figure
out what type they were.
 The types of birds had different colors, sizes, and beak shapes.
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Darwin was shocked when the ornithologist (bird
scientist) told them that all were finches.
Darwin’s Finches
Darwin’s Finches
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Darwin had also collected birds from the South American
Coastline, and he noticed some similarities.
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In Darwin’s words: “The most striking and important fact
for us in regard to the birds of islands, is their . . . close
affinity to American species in every character, in their
habits, gestures, and tones of voice”
Where did the finches come from?
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Islands, including the Galapagos, are formed by sediment
from volcanic eruptions.
 When they form, there is no life on them.
 Seeds drift from nearby, blown in by wind, and plants grow. This
makes way for animals that feed on the plants, and then animals
that feed on those animals.
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Darwin noticed that a certain species of finch regularly
flew to the island from South America, though these
finches were different from those which lived on the
islands.
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He hypothesized that the birds of the Galapagos were
descendants of birds from South America.
Why all of the different species?
• In
all places on Earth, there is a struggle for
survival.
 The environment can only support a certain number of
organisms.
 Food, water, and shelter are limited.
• Darwin
thought that the different beaks of the
finches gave them an advantage because it
allowed them to take advantage of certain food
sources available on the islands.
• As
he continued his travel, he noticed the same
trend for turtles, mammals, and other organisms.
Principles of survival
• Darwin
put all of his observations together and
came up with 4 principles of survival.
1.
Organisms can produce more offspring than can
survive.
2.
Variations, or little differences, exist in
individuals in a species
3.
Variations are passed to offspring.
4.
Organisms with variations that make them
better able to survive, will survive.
Natural Selection
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Based on these principles, Darwin published a book
called “On the Origin of Species” in which he came up
with the phrase Natural Selection to describe them.
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Natural selection-organisms with traits best suited to the
environment are more likely to survive and reproduce.
 They are then able to pass these beneficial traits on to their
offspring.
 Nature=
 Selection=
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“Nature selects” those organisms best suited to the
environment in which they live
Variations and Adaptations
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A variation is an inherited trait that makes an individual different
from other members of its species
 Can result from mutations (the beneficial types).
 These variations can be minor changes in height, color of fur, or a little larger of
a beak.
 As these traits are passed on, they become more common in the species.
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An adaptation is a variation that helps organisms survive in the
environment in which they live.
 A white bear in a snowy environment.
 Other examples?
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Camouflage is a key adaptation
 RIP Mavis
Speciation
• Recall
that a species is a group of organisms that
can breed and produce fertile offspring.
 Dogs are the same species (Labradoodle)
 Lions and housecats are not (Dinner)
• Over
time, the minor changes can become so
great that organisms are no longer able to breed
with their parent population.
 Poodles and wolves
 Can result from geographic isolation (volcanic eruption),
or from accumulations of minor changes.
 Once this happens, they are no longer the same species.
 They have split into 2 different species.
 Called speciation
Evolution
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Change in inherited traits over time.
 More scientific definition: Change in the frequency of alleles over time.
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Can be gradual (take a lot of time)
 Called gradualism
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Can be more rapid with long breaks in between
 Called punctuated equilibrium
 Equilibrium=no change
 Punctuated=scattered throughout
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Both occur often.
 Dogs descending from wolves=gradualism
 Antibiotic resistance in bacteria=Punctuated equilibrium
Evolution today
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Evolution is considered the most well-supported theory in
all of biology
 Even more evidence than the Germ Theory of Disease or the Cell
Theory
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Nothing in biology (life science) makes sense without
evolution
 Why do all organisms have cells that are so similar?
 Why do Mendel’s Laws of Inheritance apply to pea plants, as well
as all other organisms?
 Why do all living things contain DNA?
 Etc.
Evidence For Evolution
• The
most apparent evidence for evolution is the
fossil evidence
 A fossil is a remnant of a past organism
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Imprint fossil
Mineralization fossil
Frozen fossils
Fossils in amber
Cast fossils
Cool fossils
Embryology-study of development
At one point,
you had a tail!
Homologous Structures
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Homo=same
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Same bones, same place, different species.
DNA
• Best
evidence for evolution.
• All
organisms, past and present share genes on
DNA
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All humans have 100% similar DNA
Humans and chimpanzees share 98% of their DNA
Humans and mice have 80% similar
Humans and flies are 60% similar
Humans and bananas are 50%
15% with grass
7% with bacteria
When we trace DNA, similar
structures, and looks, we get this:
What if a species does not adapt?
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Conditions often change.
 Ice ages, climate change, increase in predation, humans messing stuff up,
etc.
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If a species is able to adapt to the changing conditions, they can
survive.
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If not, they die off.
 Extinction is the death of the last member of a species
 It is final. The species cannot come back
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Sometimes, many species die at the same time.
 Mass extinction=death of more than 50% of species in a short period.
 5 great extinction in the past
 Including dinosaurs
 1 occurring right now
 Way to go us…
Primate Evolution
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Humans belong to a group called primates.
 These include monkeys and apes
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Humans are apes
 Along with chimpanzees, gorillas, and orangutans
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Humans did not “come from apes”
 We are apes!