Transcript Green sea turtle in the Galápagos Islands

Bio 1010
Dr. Bonnie A. Bain
Chapter 13: Evolution
Evolution:
Change over time
Mechanism:
Natural Selection
Selection Event:
Any occurrence that kills large numbers of
the population
The survivors of the selection event are the
ones which go on to reproduce and form the
next generation
Natural Selection:
Hurricanes, floods, fires, disease, etc.
Artificial Selection:
Breeding of crops, farm animals, pets, etc.
The selection event is a human deciding
which ones to breed
Figure 1.15a
Artificial Selection
Figure 1.15b
Artificial Selection
Figure 13.1
Evolution of
pesticide resistance
in insects
Selection event:
Application of lots
of pesticide
1
Evolution of Pesticide Resistance
Pesticides often have encouraging early results
First application can kill up to 99% of all insects
The resistant survivors produce the
next generation
In each subsequent generation, there are
more and more resistant survivors
Evolution at work!
Evolution: change over time
Mechanism: Natural Selection
As a result of natural selection, a population will
change over time
Individuals don't evolve, but populations
do
Natural Selection leads to
evolutionary adaptation:
Defined as, “ a population's increase in the
frequency of traits suited to the
environment”
Adaptation can also refer to the trait itself
Example: camouflage is an adaptation that
helps the organism avoid predators
Figure 1.14a
Figure 1.14b
Figure 1.14c
Figure 1.14d
Figure 13.2
Camouflage
Figure 1.2g
Extra Photo 01.02gx2
Sea spider, Pallenoides sp.
Aposematic Coloration
The opposite of camouflage
The individual is brightly colored and
really stands out from the background
The brightly colored individual is
poisonous or venomous and can sting or
bite
Examples: bumblebee, wasp, coral snake
Aposematic Coloration in a
Monarch Butterfly
Aposematic coloration in a sea spider
Aposematic coloration in a sea spider
This species of sea spider,
Stylopallene longicauda,
lives on a poisonous bryozoan, Amathia
It eats this bryozoan and stores the
poison in its own tissues
When a fish tries to eat it, it spits the
sea spider right back out
Natural selection events, like hurricanes,
floods, fires, etc. can cause a change in
food supply for a population
This situation can also lead to the evolution
of a population
Classic example of this:
Darwin's Finches
Figure 13.14
Darwin's Finches
Galapagos Finches (Darwin's Finches)
Galapagos Islands
Lots of fairly isolated small islands
– No island-hopping—birds are too small
Each island has several finch species
Main differences among all the species:
Beak size and shape
Figure 13.4
Fig. 13-03c
Galápagos
Islands
PACIFIC
OCEAN
Pinta
Genovesa
Marchena
Equator
Santiago
Daphne Islands
Pinzón
Fernandina
Isabela
0
0
40 km
Santa
Santa
Cruz
Fe
Florenza
40 miles
San
Cristobal
Española
Fig. 13-04a
Figure 13.5a
Fig. 13-02a
Green sea turtle in the Galápagos Islands
Figure 1.13
Galapagos Finches (Darwin's Finches)
Within a population of these finches,
beaks come in small, medium, large
(population variation):
Small beaks: feed on small seeds
Medium beaks: feed on medium-sized
seeds
Large beaks: feed on large seeds
Mixed population of small, medium, and
large individuals
Smaller members of the population eat
small seeds
Medium-sized ones eat small to mediumsized seeds, etc.
A selection event occurs:
A really severe storm wipes out finch food
supply
Only plants with big hard seeds left on the
island
Only the biggest survivors (with the
biggest beaks) can eat the remaining seeds
This leads to the formation of a new species
(with a large tough beak)
Evolution in action!
Darwin observed and wrote about this when
he visited these islands
and
this has actually been observed in modern
times (1980's) by Dr. Peter Grant and his
students from Yale University
Peter Grant wrote a book on this:
“The Beak of the Finch”
Figure 1.13
Darwin's finches,
An example of
Adaptive Radiation:
The rapid formation of
lots of species
from one common
ancestor
During Darwin's voyage around the world
(as ship's naturalist on the HMS Beagle),
his ship stopped in the Galapagos for a
while and Darwin spent a long time
observing the finches
He later wrote in his journal that these
finches were one of the most important
aspects of his trip around the world since
they got him started on working out the
mechanism for evolution