BIOL 1321 LAB3

Ecological community

all interacting organisms occurring in a given space

Predation

organism feeds on another organism

Competition

2 or more organisms compete w/ each other for a limited resource

Symbiosis

any close and long-term interactions between 2 diff organisms

The communal interactions lead to…

a balance between environmental resources and the # of individuals using those resources

Example of communal interactions leading to a balance of resources?

Predators kill easy prey and leave behind prey w/ better defenses against predation

What are the forces that drive evolutionary change in populations?

• Immigration (coming in to a population)

• Emigration (moving out to a population)

• Mutation

• Predation + competition

• Natural selection

• Genetic drift

Charles Darwin

Developed natural selection as a concept (1800s)

Charles Darwin pointed out that

• Each generation, many more individuals are born than will survive to reproduce

• Populations of organisms are variable (have variety)

• Variation is inheritable

• Organisms w/ certain characteristics are more likely to survive and reproduce than those w/o

Natural selection will result in…

a gradual change in the inheritable characteristics of a population

Natural selection

Differential survival and reproduction of organisms that have advantageous characteristics 

What is differential survival?

Individuals within a population have varying rates of survival and reproduction due to differences in their traits; variation best suited to environment survives

Genes leading to camouflage can spread through…

natural selection and inheritable genes, but the process isn’t perfect; can have mismatched and well-matched individuals in a population

Creationists (christians) called the peppered moth research fraudulent because…

Real peppered moths don’t sit on trees w/ wings extended; questioned evolution

Late 1900s: Britain and other countries cleaned the air from coal smoke, making the trees go from dark to light, and…

The dark peppered moth became rare again; a liability

Biologist Michael Majerus

Conducted a massive study to see if predators were the cause of the dark peppered moth’s disappearance (2001)

What did Biologist Michael Majerus find?

After releasing 4864 moths, some dark and light, dark moths were 9% less likely to survive, or escape being eaten by birds

Natural selection

Is not the only force that can drive evolutionary change

Genetic drift

There is less variability in a smaller population, which causes certain traits to be more prevalent (population bottleneck and founder effect)

In the natural world

• Process of selection often proceeds slowly and gradually

• Significant changes may occur in a small number of generations under certain circumstances

4 diff habitats in the experiment

Sand, soil, gravel, decomposed granite

How many generations of beans were there?

4

What was the population # for each generation?

100; mixed in a 250ml flask, 80 beans were chosen and 20 survive to reproduce

What were the findings of the experiment?

For the gravel population, Garbanzo beans and Great Northern beans outlived the other beans because they blended in w/ their environment

What was the selective force in the experiment?

Predation/natural selection

What factors determined how effective natural selection was?

Adaptation (ability to blend in), reproduction, variation

What are 2 diff strategies a population of prey could take in the experiment?

Hiding further underground, or adapting to the appearance of the habitat