Populations and Species

Chapter 16

1.         Evolution: Populations

2.         Populations

            a.         Members of same species

            b.         Living in same geographic location

            c.         Individuals within population vary

3.         Normal Distribution (bell curve)

            a.         Variation of trait centered on mean

            b.         Compare traits

            c.         Graph data

            d.         Shape of graph describes population

            e.         Ideal: curve centered on mean

            f.         Skew: indicates variable affecting population

4.         Causes of Variation

            a.         Mutation

            b.         Recombination

            c.         Crossing over

5.         Frequency

            a.         Occurrences of event/total events

            b.         Flip coin 100 times, get 51 heads, frequency 51/100

            c.         Total of all frequencies is 1

6.         Allele Frequency

            a.         Divide number of particular allele by all alleles

7.         Phenotype Frequency

            a.         Divide number of particular by all phenotypes

8.         Genetic Equilibrium

            a.         Allele frequency remains constant

            b.         Phenotype frequency may change

            c.         Use 4 O’clocks as example

9.         Hardy-Weinburg Principle

            a.         5 conditions required for equilibrium

            b.         If conditions not met variation and evolution occur

            c.         No mutations

            d.         No migration

            e.         Large population

            f.         Random mating

            g.         Natural selection does not occur

10.       Effect of Mutation

            a.         Produce new alleles

            b.         Change allele frequency

            c.         Spontaneous: produce minor changes

            d.         Mutagens: produce major changes

11.       Effect of Migration

            a.         Individuals enter/leave

            b.         Gene flow

                        i.         Alleles lost

                        ii.        Alleles added

            c.         Alters allele frequency

12.       Effect of Genetic Drift (pg. 243)

            a.         Small populations

            b.         Random events

            c.         Alleles lost

13.       Effect of Non-random Mating (1)

            a.         Geographic isolation limits choice

            b.         Mates are related

            c.         Amplified occurrence of traits

            d.         Recessives more common

14.       Effect of Non-random Mating (2)

            a.         Select mate with similar genes/phenotype

            b.         Increase the occurrence of certain genotypes

            c.         No change in allele frequency

15.       Natural Selection

            a.         Descent with modification

            b.         Pressure from environmental changes

            c.         Adaptive variations fitter

            d.         Fit organisms pass on most genes

16.       Stabilizing Selection

            a.         Population fits bell curve

            b.         Average form most fit

            c.         Extreme forms die out

            d.         Population shows little variation

            e.         All members have similar morphology

17.       Directional Selection

            a.         1 extreme more fit

            b.         Average moves toward that extreme

            c.         Population curve skewed

18.       Disruptive Selection

            a.         Extremes most fit

            b.         Average individuals die out

            c.         Population tends to both extremes

            d.         Population curve develops two peaks at extremes

19.       Sexual Selection

            a.         Females select mates

            b.         Mate selected on basis of some trait

            c.         Degree of trait indicates potential fitness

            d.         Genes of successful reproducers passed on

            e.         Extreme forms of trait develop

20.       Morphological Concept of Species

            a.         Based on structural differences

            b.         Benfits

                        i.         Easily observed

                        ii.        Ready communication about characterisitics

            c.         Limitations

                        i.         Animals of different appearance mate (page 237-238)

                        ii.        Natural variation in phenotypes (page 236)

21.       Biological Concept of Species

            a.         Based on reproductive capability

                        i.         Able to breed

                        ii.        Produce fertile offspring

                        iii.       Reproductive isolation

22.       Species

            a.         A group of similar looking individuals capable of producing fertile offspring in the natural environment and reproductively isolated from other populations

23.       Cerion:

            a.         Land snails from West Indies

            b.         Two land forms

                        i.         Bank edge: raw windy, rapid drop to ocean

                        ii.        Bank interior: calm shallow

            c.         Two forms develop

                        i.         Thick shell, strong ribbed, wide, parallel sides

                        ii.        Thin shell, ribless, narrow, barrel shape

            d.         Forms predicted from bathymetry

            e.         Hybrid forms where landforms meet

            f.         Both forms same species

24.       Formation of New Species

            a.         Interbreeding prevents by isolation

            b.         Variation makes mating impossible

25.       Geographic Isolation

            a.         Physical separation

                        i.         Earthquake

                        ii.        Flood

                        iii.       Formation of island

                        iv.       Volcano erupts

            b.         Gene flow stops

            c.         Eg. Pupfish on page 310

26.       Reproductive Isolation

            a.         Heritable feature preventing interbreeding between genetically divergent populations

27.       Prezygotic

            a.         Before fertilization

            b.         Mechanisms that prevent mating or fertilization

28.       Ecological Isolation

            a.         In same local area

            b.         Adapted to different microenvironments

29.       Temporal Isolation

            a.         Same environment

            b.         Potential to interbreed

            c.         Reproduce at different times

30.       Behavioral Isolation

            a.         Courtship rituals

            b.         Only respond to own species not similar ones

31.       Mechanical Isolation

            a.         Incompatible body parts

32.       Gametic Mortality

            a.         Gametes mix but no fertilization

            b.         Chemical signals not recognized

33.       Postzygotic Isolation

            a.         Occur after fertilization

            b.         Prevent/slow development

            c.         Produce sterile offspring

34.       Zygotic Mortality

            a.         Egg fertilized

            b.         Zygote dies

35.       Hybrid Inviability

            a.         Hybrid forms and develops

            b.         Low fitness and survival rate

36.       Hybrid Infertility

            a.         Hybrid forms and develops

            b.         High survival rate

            c.         Infertile

37.       Gradual Model of Speciation

            a.         Slow incremental change

            b.         Low periods of time

38.       Punctuated Equilibrium Model

            a.         Variations carried as recessives

            b.         Sudden environmental change

            c.         Recessive now increases fittness

            d.         Rapid development of new species