Download Evolution

Evolution
Reminder
 Read chapter 22
 Darwin, Lamarck, Lyell, and Wallace
 Resistance to evolution
 Pre-Darwin views
 On The Origin of Species by Means of Natural
Selection
Introduction
Evolution – a change in the genetic makeup of a
population over time.
 Unifying theme of biology
 Studied from the molecular to ecosystems level
 Relates seemingly unrelated organisms
Overview
• Variation exists within all populations (mutation,
sexual reproduction, conjugation, etc.).
• Variations in a population are selected for (good) or
selected against (bad) depending on the situation.
• Different populations of the same species are sometimes
separated genetically, and are exposed to different
circumstances.
• The variations that are selected for or against may be
different for 2 different populations, causing the
populations to change differently.
• If the changes are significant enough new species may
occur.
You have already seen the
concepts of evolution at work.
Visible evolution
 Medicine: flu vaccine
and antibiotics
resistance
 Agriculture: hybrid
plants and pest
resistance
 Biotechnology:
transgenic organisms
Populations of species are
changing.
Ancestor
Descendent
Descendent
Mechanisms for evolutionary
change.
Artificial Selection
 Commonly
called selective
breeding.
 Selecting
organisms with
desired traits
when breeding
livestock, pets,
or crops.
Mechanisms for evolutionary
change
Natural selection
• Natural conditions
(ex. environment
and predator)
select for favorable
characteristics.
• Over generations,
the population will
change to favor
organisms with
traits that make
them more fit for
their environment.
Evidence for Evolution
• Biogeography – the geographical distribution
of species.
– Many islands have species found nowhere else
(indigenous).
– Closely related species are often found on nearest
island mass.
– Similar environments on opposite ends of the
earth do not have closely related species.
– Tropical animals of South America are more
closely related to desert animals of South America
than Tropical African animals
Evidence for Evolution
• Comparative
Anatomy
• Forelimbs of
closely related
animals have
similar anatomy
(even though they
have different
functions).
• These are called
homologous
structures.
Evidence for Evolution
 Fossil record –
shows
chronological
appearance of
different
species.
Evidence for Evolution
• Analogous structures –
Structures that have the
same function, but
different structures (ex.
Fly wing, bird wing bat
wing).
• Vestigial organs – organs
that have no function.
– Historical remnants
– Ex. Whale has remnants of
leg bones, appendix in
humans, leg bones in
snakes.
Dolphin with legs?
Evidence for Evolution
• Comparative
Embryology
• Closely related
species go through
similar developmental
stages.
• Ex. Gill pouches and
tail are found in most
vertebrates.
Evidence for Evolution
• Molecular biology
– DNA and protein analysis
show relationships
between species.
– Closely related species
have similar sequences of
bases in DNA and have
similar proteins.
– Ex. Humans and
chimpanzees have 96 –
98% identical DNA.
– Humans share less DNA
similarities with dogs, and
even less with lizards.