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Paleo-4 Notes
Darwin & Evolution
What is evolution?
What is a species?
Differentiate between a
variation and an
adaptation?
evolution - change in the hereditary characteristics of groups
of organisms over the course of generations. (Darwin called
this process "decent with modification".)
species – a group of similar organisms that can mate with
each other and produce fertile offspring.
variation - genetically determined differences in the
characteristics of members of the same species.
adaptation – a trait that helps an organism survive and
reproduce.
The Theory of Biological Evolution draws on evidence of
observations of the fossil record, genetic information, the
distribution of plants and animals, and the similarities across
species of anatomy and development.
The Darwin Story
The Gathering of Observations
The Trip Begins– December of 1831 the HMS Beagle leaves
England for a 5 yr. Voyage around the world with 22 year-old
Charles Darwin who became the ship’s naturalist.
The Observations:
- In Brazil: insects that looked like flowers, and army-like
ants.
- In Argentina: armadillos, sloths and bones that resembled
the sloth, but with variations
- In the Galapagos Islands:
- giant tortoises with different shells on different islands
- seals covered with fur
- lizards that only ate prickly cacti
- small differences in birds of the same family
- plants that were similar to those he’d collected on the
mainland.
- cormorants on the mainland - could fly / on the island -
Name one example of
adaptations Darwin
observed during his
voyage on the HMS
Beagle?
What is Darwin’s theory of
natural selection? What
does his theory have to do
with the term evolution?
What other scientist had
similar ideas to those of
Darwin?
Darwin proposed that
changes in organisms
occur continuously and
slowly over time – called
gradualism. 100 years
later, after many scientists
have examined the fossil
record, Gould & Eldredge
proposed a different
theory. What was it called
and how did it differ from
gradualism?
couldn’t
- differences in the claws of iguanas
- finches with 14 variations in beaks for different foods
The Theory – After he got back to England, Darwin consulted
with other scientists about what he saw for over 20 years
before he published his theory of natural selection, The
Origin of the Species, in 1859. Darwin discovered that the
idea of natural selection ( a process by which individuals that
are better adapted to their environment are more likely to
survive and reproduce) was not exclusively his. Alfred Russell
Wallace (1823-1913), a young naturalist, had developed
similar ideas in an essay called "On the Tendency of Varieties
to Depart Independently from the Original Type." Wallace
sent this paper to Darwin for an opinion. Darwin took
Wallace's manuscript to a friend, Sir Charles Lyell, who
decided that both Wallace's and Darwin's ideas should be
presented at the same time. On July 1, 1858, both papers
were read at a meeting of the Linnaean Society of London.
They felt biological evolution took place gradually.
In recent years, Gould & Eldredge's "punctuated
equilibrium" theory proposes that the changes happen more
rapidly due to “catastrophes in the environment.
Gradualism
What three factors can
affect natural selection?
Punctuated Equilibrium
3 factors affecting Natural Selection:
1) Overproduction – not enough resources (food, water, etc.)
for the number born.
2) Competition – those who don’t get the limited supplies of
food and water die.
3) Variations – a difference between individuals of the same
species.
The role of genes in evolution of organisms was unknown to
What role do genes play in Darwin. It was almost 100 years before scientists discovered
evolution?
that these changes could come from gene mutations of
shuffling of alleles during meiosis.
What is one way a new
species could form?
How do new species form? One way is by geographic
isolation of a species, where a species could be separated
into two different environments on a local level (disasters) or
worldwide (plate tectonics).
Summaries