Evolution, Pattern and Process

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Evolution by Natural Selection

Change of allele/gene abundance in a population is the fundamental evolutionary change.

Speaker Notes:

All change is NOT biological evolution. Differential success in reproduction (natural selection) is an essential part of biological evolution.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Reading Assignment

The reading for today’s lecture is chapter 24.
Focus attention on the ‘Key Concepts’.
Know major historical features of evolution which lead to the formulation of the idea.

Speaker Notes:

Evolution, a ‘top ten’ idea

The idea that species change and that they change because of natural selection is one of the ‘top ten’ ideas of understanding the world.
Pattern can be understood as historical evidence, process should be looked at as the mechanism.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Speaker Notes:

Evolution, the pattern

Fossils provided evidence of
- The many million years the earth existed
- The extinction (disappearance) of species
- The existence of many transitional forms among fossils
- Biogeography
- Homology

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Speaker Notes:

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Historical Evolution

Darwin proposed:
- Species changed gradually thru time
  - “descent with modification”
- New species had arisen many times in the history of the earth
- Species that had existed were extinct

Speaker Notes:

At the time of Darwin people did not accept the idea of extinct species. They thought that everything God had created would exist forever. Some creationists will say fossils were planted by God to ‘trick’ people, but a tricky God is not desired by most people.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Hierarchy of species

Taxonomic hierarchy of Linnaeus is consistent with the notion that species change continually and irreversibly.
Biogeography, that fact that species within a continents were often more similar to each other than they were to species different continents was consistent with “descent with modification.”

Speaker Notes:

Carnivore and herbivores of South America share similarities with each other rather than with carnivores and herbivores of Asia or other areas.

Extinction

Few children do not know of dinosaurs. Dinosaurs are all extinct.
The passenger pigeon was once the most abundant bird in North America. It is extinct.
Many more species are extinct than are currently extant.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Speaker Notes:

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Homology

Though originally based on similarities of hard parts like bones, homology is currently studies almost exclusively through comparison of DNA sequences.
Comparison of sequences
- Alignment
- Counts of differences (the difference matrix)

Speaker Notes:

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Evolution, the process

A necessary and sufficient condition for biological evolution is change of gene frequency/abundance in a population.
Necessary means that without gene frequency change there is no evolution.
Sufficient means that if gene frequency changes then biological evolution has occurred.

Speaker Notes:

Differential survival of genes. Genes/alleles which are passed on to the next generation.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Evolution is logical

Once we except that:
- Not all phenotypes are equally likely to be represented in next generation because some function better than others,
- AND that phenotypic differences often have a genetic basis,
Then we have EVOLUTION.

Speaker Notes:

Would you deny differences in function or the genetic basis of differences in function if you advocate Intelligent Design?

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Selection that is not evolution

Selection implies differential survival according to phenotype.
If phenotypic differences do not have a genetic basis, then the differential survival will not result in any change in the genotype frequencies of the next generation.
No genetic change in composition of population means no evolution.

Speaker Notes:

My father’s heart was damaged by rheumatic fever when he was a child. His live span was not long. Rheumatic fever is an environmental condition for which there is no evidence of genetic resistance. My father’s early death does not predict my demise at a young age because the damage to his body was not dependent on his genes.

Adaptation, selection that is evolution

Biologists use the term adaptation for the condition where a gene increases in abundance, because it has a better function in the environment.
Adaptations increase fitness (p491)

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Speaker Notes:

Camouflage

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Speaker Notes:

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Gene frequency change whose basis is unknown

If gene frequency changes, a population has evolved, even if we do not understand the basis for the change.
You will learn that phylogeny is primarily based on the accumulation of genetic changes that have no functional differences (equivalent alleles are said to be neutral).

Speaker Notes:

Functionally equivalent = neutral

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Human Evolution

Humans are NOT derived from chimps. Chimps and humans share a common ancestor. Both chimps and humans changed since that time.
The DNA sequence of Neandertal man is 63% complete. Neandertal is an extinct species of Homo.

Speaker Notes:

P762-766 describe a modern view of human evolution

Exam 2 Lecture 6

UIC BioS 101 Nyberg

EVOLUTION TODAY

Understanding evolution is crucial to understanding medicine and agriculture

DISEASES become resistant to antibiotics used to kill them
INSECTS become resistant to pesticides used to kill them

Speaker Notes:

Creationists often acknowledge that ‘microevolution’ is a reality but insist that new SPECIES are not explained by microevolution. In reality species are defined by people and new species are arising every day by taxonomists.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

EVOLUTION OF ANTIBIOTIC RESISTANCE

As an antibiotic comes into widespread use there are more opportunities for resistant mutants to arise.
Resistance does not have to arise independently in each bacterial species. Lateral gene transfer is often the mechanism of spread of resistance.

Speaker Notes:

Gonorrhea is an STI that is resistant to many antibiotics.

Drug resistance in bacterium that causes tuberculosis

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Speaker Notes:

Exam 2 Lecture 6

UIC BioS 101 Nyberg

PESTICIDES

The evolution of resistance to pesticides by the “target” insects has occurred in many species.
Integrated pest management attempts to reduce the likelihood of evolution of resistance.

Speaker Notes:

The change in human practices is based on an increase in knowledge which is distinct from natural selection.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Species are changing

Besides the disease/pest cases already presented,
morphology change in Galapagos finch respond to events.

Speaker Notes:

How much change is necessary to recognize a new species? Most biologists use any detectable difference as sufficient.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Evolution is not directed?

Aristotle and others portrayed evolution as directional and irreversible.
Modern biologists acknowledge that complexity and efficiency tend to increase, but point out that reversals of function do occur and that not all traits are adaptive.

Speaker Notes:

It is impossible to measure the attributes of organisms that existed more than a million years ago. If we could, my guess is that in most cases they would function better.

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Fitness Defined

Absolute fitness (for a specific time period) = abundance at later time/abundance at earlier time.
Relative fitness (for a specified time period and when there are at least two types) of A to B = absolute A / absolute B

Speaker Notes:

Fitness is a measure of biological ‘success’ and is much commonly encountered as differential success (which requires at least two different types).

Exam 2 Lecture 6

UIC BioS 101 Nyberg

Vocabulary

Allele frequency
Necessary
Sufficient
Differential survival
Extinct

Extant
Biogeography
Adaptation
Homology
Resistance to biocides
Fitness

Speaker Notes: