Transcript The Evolution of a Species

The Evolution of a
Species
How does a species evolve?
-The evolution of a new species is called
speciation.
-A species are organisms that look alike and
can have children with each other.
-Speciation happens when organisms in a
population can no longer mate with each
other to produce fertile offspring
(children).
-Fertile means to be able to have children.
How does speciation happen?
1. Geographic isolation-a
physical barrier divides a
population. The
separated members of
the population can no
longer breed and over
time, develop different
genes and become
different species.
How does speciation happen?
2.
Reproductive Isolation-species
cannot mate with each other due to
differences in DNA, different mating
seasons or different # of
chromosomes. Polyploidy is when
the # of chromosomes doubled.
Geographic or Reproductive
Isolation?
Geographic isolation
How much time does it take to
develop a new species?
-Speciation takes a long time. There
are 2 theories of speciation.
1. Gradualism-the idea that
species develop slowly over a long
period of time.
2. Punctuated Equilibrium-the
idea that species don’t change over a
long period of time, and then there is
rapid change in a species
Gradualism or Punctuated
Equilibrium?
Camel Evolution
Age
Organis
m
Skull and
teeth
Limb
bones
Paleocene Eocene
65 million 54 million
years ago years ago
Oligocene
33 million
years ago
Miocene
23 million
years ago
Present
Gradualism
Gradualism or Punctuated Equilibrium?
Loxodonta
africana
Elephas
maximus
0
1
2
Elephas
3
4
Mammuthus
primigenius
Loxodonta
Mammuthus
5
Primelephas
6
Ancestral species
about 55 million years ago
Punctuated Equilibrium
Patterns of Evolution
Convergent evolution-species evolve to
look alike. Ex: Dolphins and sharks.
Divergent evolution-one species turns
into many species. Ex: one bird to
many birds.
Convergent or Divergent
Evolution?
Divergent Evolution