Variation, Selection & Evolution in Plants

I. Evolution by Natural Selection

A. Charles Darwin, Alfred Russel Wallace

-Origin of Species (1859)

that last paragraph!

1. What is evolution?

• all species are related by descent from a common ancestor
• species diversity is a consequence of change through time by natural selection: "descent with modification"

2. What is natural selection?

• individuals vary: example of persimmon seeds and seedlings

• some traits are heritable
• not all offspring survive
• natural selection not random-certain traits can help an organism to survive and reproduce more

B. Evidence for Evolution and Natural Selection

1. What is the evidence that species are related and not independent entities?

-Biogeography (Distribution of species)

-not just environment that determines where organisms are found

 Galapagos islands  Galapagos finches adaptive radiation

2. Evidence species have changed through time.

-fossil evidence

-vestigial traits

3. Evidence for natural selection

-natural selection is ongoing: ecotypes in Achillea glandulosa

4. Evidence from molecular biology

-molecular biology

C. What is the basis of heritable variation in populations?

1. mutation mutation2 transposons

2. genetic recombination

D. Speciation

How does it come about?

1. Factors that act on a population gene pool

POPULATIONS EVOLVE NOT INDIVIDUALS

Allopatric or geographic speciation

Sympatric or "same place" speciation

Types of Species:

Organisms are different species when:

• Biological Species Concept - they cannot interbreed
• Morphospecies Concept - they are different morphologically and do not come in contact for interbreeding

2. Polyploidy (sympatric)

Gamete formation depends on the presence of homologous pairs in meiosis

polyploidy can make "true" hybrids fertile

sunflowers in American west: Helianthus annus X H. petiolaris = H. anomalis

II. Artificial Selection

A. Inbreeding

-Self-pollination or inbreeding desirable cross-pollination

-How to make a hybrid

-"hybrid" strains

B. Asexual reproduction

-cuttings

-grafting

-tissue culture

-genetic engineering

III. Plant Systematics/Taxonomy

A. Early History

1. Theophrastus (370-287 B.C.)

-Enquiry Into Plants

2. Dioscorides (first century A.D.)

-Materia Medica

3. The Herbalists (Renaissance)

-Doctrine of Signatures

Hepatica acutiloba; Pulmonaria officinalis; Ranunculus ficaria; Sanguinaria canadensis 1 2

4. Carolus Linneaus (1707-1778)

-Species Plantarum

flower structure

B. How are plants named?

1. common name

2. scientific name

3. taxonomic hierarchy