Evolution
Sections 15-1 & 15-2
Life’s Diversity
On Earth there are millions of different types of organisms = biological diversity
What is a Theory?
In science, the word theory takes on a new and very different meaning.
A scientific theory is…
• Testable
• Well-supported
• Based on facts, observations, and hypotheses
Evolution Why is there so much biological diversity?
evolution = change over time Process of by which modern organisms have
descended from ancient organisms
Lamarck
First person to propose a theory of evolution.
Law of use and disuseAn organism can lose or change a body
feature during its life time and passes it on to their children
1. Using it -improves2. Not using it - disappear
•short-neck giraffes stretched their necks to reach higher into trees for food = acquired longer necks
•this acquired characteristic was passed on to (inherited by) their off-spring
Lamarck
evolution affects individuals the individuals evolve
environmental changes cause evolution Area with short flowers and hummingbirds with short beaks , now
starts to grow long flowers instead
organisms change in response to the environment
Hummingbirds with short beaks start to develop long beaks all organisms survive
those with short beaks will develop long beaks in time to be able to survive
Charles Darwin
Disproved Lamarck’s theory of evolution
Darwin’s new theory was based on …
natural selection
Charles Darwin sailed on the Beagle around the world.
Voyage of the Beagle made observations, collected fossils, living
organisms, and studied the Earth
Some fossils looked like living organisms while others looked foreign
The Importance of Fossils Darwin asked important questions as he
collected the fossils.
Why had so many species disappeared?
Are these fossilized species related to living species?
What other important info do fossils hold?
The Galapagos Islands Islands were close together but had very
different climates Darwin studied the animals on the islands
Darwin
evolution affects populations Not just individual
environmental changes cause evolution Same as Lamarck
organisms with certain features are naturally selected
hummingbirds with slightly longer beaks are naturally selected for
certain organisms survive hummingbirds with the longer beaks will survive.
Darwin explained evolution by
NATURAL
SELECTION
Mutations
A change in the DNA code, that forms a new trait
Can be good = increase survival Can be bad = decrease survival
Darwin’s Findings
Adaptation A beneficial trait (good mutation) that helps an
organism survive and reproduce
Adaptations evolve (develop or change over time) (1000’s years)
Anatomical - Teeth, body covering Physiological - movement, camouflage, mimicry
Adaptation?
My partially webbed hind feet help me to swim.
My flattened tail acts as a rudder.
My teeth help me to shred cattails and other plants to build my lodge. Sea otter
Adaptation?
My hard outer shell helps to protect my soft body from predators.
I can make my own cement to attach myself to stationary objects.
I have feathery legs for trapping plankton and other food.
Barnacles
Adaptation?
My long beak helps me to drink the nectar from plants.
My wings help me to hover in one place.
My small body is lightweight.
Hummingbird
Behavior adaptations can be learned or instinctive.
1. Social behavior - some animals live by themselves,
while other live in groups. 2. Behavior for protection - can help to protect the
animal. For instance the opossum plays dead. A rabbit freezes when it thinks it has been seen.
• Migration (birds, whales) • Hibernation (bats, snakes, bears)
Artificial Selection
Aka selective breeding
humans choose attractive matescattle ranchers choose biggest and
healthiest cowsFarmers choose biggest tomatoes
Natural Selection
Nature selects the best traits best traits survive Survive and reproduce = fitness “survival of the fittest”
4 points of Natural Selection "survival of the fittest"
1. Variations exist among members of a population
2. Many more individuals are produced than will survive
3. Members of a population compete for food, space, mates...
4. Individuals that are better adapted survive & reproduce
Evidence of Evolution
1. Fossils2. Bio-geographical 3. Anatomical 4. Embryological 5. Biochemical
1. Fossils
2. Biogeographical
Geographic Distribution of Living Species
? why similar species lived in different locations?
3. Anatomical
Homologous Body Structures
• (definition) different mature forms, but develop from the same embryonic tissues.
• means they all had a common ancestor.
4. Embryology
In the early stages of development, the embryos of many different species look very similar.
Means = a common ancestor!
5. Biochemical
same basic biochemical moleculesDNA, ATP, enzymes ...
Similarities in amino acid sequences (DNA codes) means = a common ancestor
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