Chapter 10 Biology


 Populations Change Over Time--- Evolution


Each Species- (Can Breed and Produce Healthy Offspring)

Contains Variation- Slight differences Caused by Mutation - not as important, but is a factor of variation


Recombination- from meiosis- both crossing over, independent assortment

 and combining egg and sperm during fertilization

 Variation can be subtle or dramatic like size, coat color


Due to these slight variations, an organism can adapt to its' environment

 Adaptation- advantages to one's survival in a particular environment

Due to Adaptations, organisms often become suited to a specific habitat or

 Niche includes all environmental factors to which the organism is adapted to such as light, space, temperature, what an animal eats, how it raises its' young ...

 This can cause Competition which eventually proves one population to be better adapted to drive away the competition

 Biodiversity- abundance of species that make up a biological community which includes a variety of Niches

Change is a big factor for survival

 When a change occurs in a Niche, some organisms are better suited and some are at a disadvantage

It is better for your population to be able to adapt over being highly specialized.

Are we losing Biodiversity? Explain


We study fossils to find the answer to this question, some soft bodied organisms do not fossilize well


Paleontologists study these fossils which is not complete so they must form theories based on correlations

 10.2 Evolution-Change over Time

Bonnet- To explain biodiversity he theorized periodic catastrophes explained changes in
fossils to modern organisms

Evolution- Change Over Time

Lamarck- 1. Organisms strive to improve themselves

               2. Structures that are the most used develop and others unused waste away

               3. acquired characteristics- pass on learned traits

Charles Darwin- 1831 HMS Beagle- ship to study plant and animal samples

 He studied birds from the Galapagos Islands- finches

 Darwin found that each bird had its own niche and were different species

 He then hypothesized that adaptations of animals to their environment could emerge new species

 Thus Natural Selection- survival of the fittest

 1. variation exists in a population

 2. some variations are favorable to that environment

 3. not all young produced can survive

 4. individuals that survive and reproduce are those with favorable variations

Gradualism- new species evolve as the genome of two populations

Punctuated Equilibrium- populations remain genetically stable for long periods of time, interrupted by brief periods of rapid genetic change

 explains gaps in the fossil records

Fossils- evolution does not follow a straight line

Ways to compare relatedness

 Homologous Structures- the structures have the same origin not always the same function (human arm---whale fin---bat wing)

Analogous Structures- the structures have a similar function and a different origin

 (insect wing and bird wing)

 Vestigial Structures- inherited structures that are reduced in size and often unused (hip and leg bones in a python)

 Living History - gill slits in embryos


 Evolution does not occur in a straight line- no goals to strive towards

Degree of Relatedness can be determined by:

 1. Homologous Structures-

 same origin, same ancestor

 human arm, bat wing, whale fin


2. Analogous Structures-

different origin, similar function

 insect wing, bird wing


3. Vestigial Structures- inherited, reduced in size, often unused--- pythons have vestigial hip and leg bones

 Additional information can be obtained by embryos, DNA

evidence- gene sequences



 Speciation- evolution of one or more species from the same ancestor

 can be caused by isolation from their original population

 once separated they can not interbreed and separate species can

arise -- reproductive isolation


Due to Speciation, these new species may go through different processes of evolution

 Divergent Evolution- different environments, different variations

were favorable, cause different genomes to arise the new species

that arise are no longer able to breed


Convergent Evolution- species that live in the same environment

 often adapt to one another and become closer due to surviving

 similar environmental conditions


Adaptive Radiation- evolution of many diversely adapted species

 Darwin observed this in his finches



 Populations- smallest unit which evolution takes place

 Changes in the Gene Pool- all of the genetic material of all of the

members of the population

 Allele Frequencies- number of each allele is a fraction of all genes for a

particular trait


P + Q = 1 P + 2PQ + Q = 1 Hardy Weinberg Principle


If all of the alleles are in constant state of allele frequency then they are

 said to be in genetic equilibrium

 If these conditions are not met, the equilibrium is disrupted

 1. no natural selection

 2. random mating

 3. no mutation

 4. no migration

 5. very large population


Genetic Equilibrium can be affected by chance changes in allele frequencies

 by random change due to chance events- Genetic Drift

 1. Migration

 2. Disasters

 This has a greater effect on small populations fewer than 100 individuals


Bottlenecking- genetic drift after a random reducing population event

 reduces genetic variation

 Scientists study variation and distribution of variations in a population

 If after several generations, this distribution might shift to an extreme

 phenotype---- Directional Selection


If the most common phenotype is not favored the shift is ----Disruptive Selection


Peppered Moth- Industrial Revolution changed the color of the trees and natural selection favored the peppered moths more white were easily seen and the darker moths