Download Evidence of Evolution

• Bellwork:
• Pull out Natural Selection Lab Summary
for me to read.
• Work on Butterflies
• What is Evolution?
• Natural Selection
• Evidence for Evolution
Evidence for Evolution
• The degree to which species are related
depends on how closely in time they
diverged, or split, from their common
ancestor.
• Evidence for Evolution comes from 6
areas
1. Fossils
• Although the fossil record is incomplete,
it contains many examples of fossil
sequences showing close ancestral
relationships.
The fossil record
indicates that
different species
of similar
organisms often
overlapped with
each other.
EX: Horses
Comparative Anatomy
• Comparative anatomy is the study of
similarities and differences among
structures of living species.
• By comparing anatomy of different
species, scientists are able to find clues
as to how organisms are related.
2. Homologous Structures
• Homologous structures are body parts
of organisms that are similar in structure
and position but different in function.
The forelimbs of these species are different
sizes, but their placement and structure
suggest common ancestry.
Evidence for Evolution
(cont.)
How do homologous
structures provide evidence
for evolution?
3. Analogous Structures
Body parts that
perform a similar
function but differ
in structure are
analogous
structures.
– These structures
developed independently
of one another. They are
made of different
materials and have
different structures,
however, both fly.
– These organisms did not
have a common ancestor
with wings, but both
developed wings over
time.
– It illustrates that
organisms can change
over time.
4. Vestigial Structures
Vestigial structures are body parts that
have lost their original function through
evolution.
The presence of these structures suggest that
they once used them, but have changed so
they no longer need them. If they did not need
these structures at one point in their
evolutionary past, then why have them?
Evidence for Evolution
(cont.)
How are vestigial structures
evidence of descent from
ancestral species?
5. Embryology
The science of the development of
embryos from fertilization to birth is
called embryology.
embryology
from Greek embryon, means
“to swell” and from Greek logia,
means “study of”
The remarkable similarity among with similar
structures that not all exhibit as adults
suggests they once had a common ancestor.
Evidence for Evolution
(cont.)
How do pharyngeal pouches
provide evidence of
relationships among species?
6. DNA
• Molecular biology is the study of gene
structure and function.
• Discoveries in molecular biology have
confirmed and extended much of the
data already collected about the theory
of evolution.
• Scientists can study relatedness of
organisms by comparing genes and
proteins among living species.
Evidence for Evolution
(cont.)
How is molecular biology used
to determine relationships
among species?
Evidence for Evolution
(cont.)
• Scientists have found that some
stretches of shared DNA mutate at
regular, predictable rates.
• Scientists use this “molecular clock” to
estimate at what time in the past living
species diverged from common
ancestors.
Molecular data
indicate that whales
and porpoises are
more closely related
to hippopotamuses
than they are to any
other living species.
The Study of Evolution Today
• New evidence supporting the theory
of evolution by natural selection is
discovered nearly every day, but
scientists debate some of the details.
• New fossils that have features of species
that lived both before them and after
them help scientists study more details
about the origin of new species.
Many scientists think that natural selection
produces new species slowly and steadily.
Other scientists think species exist stably for
long periods, and change occurs in short bursts.