Transcript Chap 6 - Maria Regina School

Chap 6
Evolution
• Species- a group of organisms that share
similar characteristics and can reproduce
among themselves to produce fertile offspring
• Evolution- the change of the inherited
characteristics of a species over time
Charles Darwin
• On a journey exploring the South American coast, Charles
Darwin recorded observations about the plants and animals
he saw
• He hypothesized that the plants and animals on the
Galapagos Islands originally must have come from Central and
South America, but the islands were home to many plants and
animals he had never seen there
Darwin
• Observed 13 species of finches
on the Galapagos Islands
• All 13 were similar, except for
differences in
– Body size
– Beak shape
– Eating habits
• He reasoned that the finches
must compete for food.
Finches with beak shapes that
allowed them to eat available
food allowed them to survive
longer and produce more
offspring than finches without
those beak shapes
Darwin
• Developed a theory of evolution based on his
observations and experiments
• Described his ideas in book On the Origin of
Species in 1859
• His ideas on evolution still accepted today
Natural Selection
• Organisms with the traits
best suited to their
environment are more
likely to survive and
reproduce. Their traits are
passed to their offspring
• Members of a large
population compete for
living space, food, and
resources. Those best able
to survive are more likely to
reproduce and pass on their
traits to next generation
Variations
• Variations- an inherited trait that makes an
individual different from other members of its
species
– Result from permanent changes, or mutations, in
organism’s genes
– Over time, more and more individuals may inherit
these variations, and if they continue to survive
and reproduce, can create new species
Adaptations
• Any variation that makes an organism better
suited to its environment
– Can involve organism’s color, shape, behavior, or
chemical makeup
– Ex: camouflage
• This video describes the journey of Charles
Darwin and showcases the animals he studied
HOMEWORK 2/10
• What adaptations would be helpful for an
animal that moved to the Arctic?
Geographic Isolation
• Sometimes mountains, a lake,
or other geographic features
isolate some individuals from
the rest of the population.
• Over several generations,
variations that were not
present in the main population
become more common in the
isolated group
• Over time, the two groups
may become so different that
they can no longer breed with
each other, therefore
becoming two different
species
Speed of Evolution
• Gradualism- describes evolution as a slow,
ongoing process by which one species
changes. A continuing series of mutations and
variations over time will result in a new
species
• Punctuated equilibrium- rapid evolution
comes about when the mutations of a few
genes results in the appearance of a new
species over a relatively short period of time
Clues about Evolution
• Scientists can use fossils to study organisms no
longer present on earth
– Can also determine age of organism from the rock
• Using this information, scientists can piece
together how current animals and plants may
have evolved from their ancestors.
Fossil Record
• Sedimentary rock- formed when layers of sand, silt,
clay, or mud are compacted and cemented together, or
when minerals are deposited from a solution.
• Radioactive element- gives off steady amount of
radiation as it slowly changes to nonradioactive
element. Each one gives off radiation at a different rate
– Scientists can estimate the age of a rock by comparing the
amount of radioactive element with the amount of
nonradioactive element in the rock
More Clues about Evolution
• Evolution can be viewed directly through
1. cross breeding plants to produce genetic
changes
2. Antibiotic resistance in bacteria
3. Pesticide resistant insects
• What is similar about these three examples
that allows us to view evolution directly?
Embryology
• Embryo- the earliest growth stage of an
organism
• Embryology- the study of embryos and their
development
– What conclusions can you draw from this picture?
Homologous Structures
• Homologous body parts- body parts that are
similar in origin and structure. Can also be
similar in function. Indicate that species share
common ancestor
Vestigial Structures
• Structures that don’t
seem to have a function
– Human appendix not
used, but used to have
similar function to a
cecum, a part of the
digestive track of many
mammals
• Provide evidence for
evolution
– We know snakes used to
have legs because they still
have pelvic bones ( a
vestigial structure)
MATERIAL FOR QUIZ ENDS HERE
LAB
• Complete the pedigree tutorial on
http://www.phschool.com/atschool/phsciexp/
active_art/pedigree/index.html
• Due Tuesday February 23, complete a
pedigree of your family tree that tracks
whether or not your family members can roll
their tongue.
– Must include your parents and siblings
– Can be done on computer or hand drawn
Dad
Mom
Mr.
Powers
Mrs.
Powers
Jen
Jimmy
Kerry
Danny
Henrik
Amalia
Pedigree Key
Girl, can
roll
tongue
Boy, can
roll
tongue
Boy,
can’t roll
tongue
Girl,
can’t roll
tongue
Girl,
carrier
Boy, carrier
Dad
Mom
Mr.
Powers
?????
Mrs.
Powers
????
Kerry
Jimmy
Jen
Danny
Henrik
Amalia
Is it possible for Mr. and Mrs. Powers to have children that can curl their tongues?
First, we have to figure out the Powers’ possible genotypes. To do that, we must create
a Punnett square for Mom and Dad
T
t
Tt
tt
t
Tt
t
tt
Dad
Mom
Mrs.
Powers
Mr.
Powers
Jen
Danny
Jimmy
Kerry
Henrik
Amalia
Mrs. Powers must be heterozygous! But we have no idea what genotype Mr. Powers
has. What genotypes are possible?
Tt or TT! Because both of these display the phenotype of not being able to curl tongue!
Now, we must create a punnett square for both possible phenotypes.
T
TT
Tt
t
TT
Tt
Tt
tt
T
T
TT
T
T
t
Tt
t
Dad
Mom
Mrs.
Powers
Mr.
Powers
Kerry
Jen
Jimmy
Danny
Henrik
Amalia
Can the Powers have a child that can curl his or her tongue?
Yes, as long as Mr. Powers is heterozygous for the trait.
T
TT
Tt
t
TT
Tt
Tt
tt
T
T
TT
T
T
t
Tt
t
There is a 25% chance of having a child that can curl his or her tongue if Mr. Powers is Tt.
Primates
• A group of mammals that
include humans, monkeys,
and apes
– All have opposable thumbs,
binocular vision, and flexible
shoulders
• Hominids- 4-6 million years
ago, humanlike primates
that ate both meat and
plants and walked upright
on two legs. A larger brain
separated them from the
apes
Early Humans
• Lucy- one of the oldest hominids discovered. Had
humanlike jaw and teeth, a small brain, but walked
UPRIGHT.
• Homo sapiens- evolved about 400,00 years ago. Two
groups
– Neanderthals- short, heavy bodies, with thick bones, small
chins, and heavy browridges. Lived in caves and used tools.
Probably not direct ancestor of humans
– Cro-magnon humans- similar physical appearance to
modern humans. Lived in caves, made stone carvings,
buried dead. Painted animals and people on cave walls.
Thought to be direct ancestors of modern humans
Homo Sapiens
Neanderthal
Cro-magnon