Transcript 3 Darwin Presents his Case

15 – 3 Darwin Presents His Case
Biology
Pgs 378 - 386
Baker
The Findings – The Origin of Species by
Means of Natural Selection
#6
Published in 1859 – 30
years after Darwin’s
voyage on the HMS
Beagle.
In Darwin’s book he
assembled the evidence
supporting evolution and
he proposed a hypothesis
to explain how evolution
occurs.
Of Farmers and Pigeons
Upon Darwin’s return
from his voyage he
extended his thinking
about organisms to
observations of farm
animals and agricultural
crops in England.
No Two Alike
Artificial Selection
No Two Alike
Plant and animal
breeders told Darwin
that no two plants or no
two animals were
exactly alike.
Some plants produced
more fruit and some
cows made more milk.
Artificial Selection
#7
Farmers were doing this by
picking only the largest hogs,
fastest horses and the cows that
gave the most milk to breed.
Nature provided variation and
in artificial selection the humans
intervene and decide which
organisms will produce
offspring.
Selection in Nature
Variation in Nature
Struggle for Existence
Natural Selection
Variation in Nature
The variation in nature that
Darwin observed was not linked
to Gregor Mendel’s principles
on genetics until later since
Mendel’s work was not
published until 1866.
Variation is common in nature
and in areas where humans
control the reproduction.
Competition & Fitness
Competition is present
among members of
the same species.
Those that are able to
win in this struggle
survive to reproduce
offspring.
Struggle for Existence (fitness)
#8
Darwin related Malthus’ thinking
regarding high birth rates and
decreasing resources to the
struggle for existence.
The fastest predators catch
the most prey and the best
camouflaged prey escape
being hunted.
Natural Selection
#9
Survival of the fittest.
The animals that are the
most fit will survive to
reproduce.
Over time generations
become better suited to
survive in their environment.
Descent with
modifications?
#10
Each living
species has
descended,
with changes,
from other
species over
time.
Common Descent
#11
Darwin proposed that
organisms were not
spontaneously produced as we
know them.
If you were able to trace back
far enough all living things
share a common ancestors.
Evidence of Evolution
#12
Fossil Records – different species have been present
at different times.
Geographic Distribution of Living Species – Places
with similar ecological conditions have animals that
share common features.
Homologous Body Structures – Different types of
body parts sharing the same basic structure.
Embryology – Patterns at which various embryonic
cells appear in various vertebrates.
#13 Charles Darwin’s theory of
evolution:
Variation – Individuals are different.
Overproduction – Organisms produce more
than can survive.
Struggle for existence – compete for
resources.
Species change – Individuals best suited for
their environment live to reproduce and
others die off.
New species form – All organisms came
from a common ancester.
Evolutionary Theory
#14
Strengths – insight into
biological & biomedical
sciences.
Weakness –
mechanism by which a
new species may arise
is unknown.
Common Misconception: