Lecture Two

Macroevolution

Natural Selection

Observations:

1. Variation is

characteristic of every

group of organisms.

2. More organisms are

born than survive.

Hypotheses:

1. The Struggle for

Survival

Competition for food

and/or space

Thomas Malthus

“On Population”  1798

2. Survival of the

Fittest

3. Inheritance of

Advantageous Traits

The population is the

basic unit upon which

the forces of evolution

operate.

A species is a group of

similar organisms that

actually or potentially

have the ability to

interbreed.

A population is a group

of organisms of the same

species that are actually

living and breeding

together.

balanced polymorphism

adaptive radiation

divergent evolution

convergent evolution

Mechanisms of Species

Formation:

1. Isolation

2. Hybridization

1. Isolation

reproductive barrier

geographic or physical

genetic isolation

ecological isolation

   different habitats

   different activity patterns

          nocturnal

          diurnal

          crepuscular

2. hybridization

     fertile hybrids

     nondisjunction

     polyploidy

About half of all plant

species are polyploid.

potato (Solanum)  N = 12

24, 36, 48, 60, 72, 96,

108, 120, 144

Spartina alterniflora    70

Spartina stricta    56

N = 7

Townsend’s Grass

Spartina townsendii    126

the harem effect

taxonomy

binomial nomenclature

both words are always in

Latin and are printed in

italics or underlined

Genus species

Carl Linnaeus

Linnaean System

systematics

Kingdom

Phylum  (plural: phyla)

Class

Order

Family

Genus (plural: genera)

Species (plural: species)