BIO 80 Exam 1

What is Biology?

scientific study of life

What is science?

both a body of knowledge & a process

• Ongoing & never ending

• Global human endeavor

• Takes many forms

• Exciting

scientific facts

objective & verifiable observations that have repeatedly been confirmed

Theory

well-substantiated explanation of some aspect of the natural world

Scientific method

Hypothesis-driven science both asks & answers questions

Steps of scientific methods

-observation

-questions

-hypothesis & predictions

-experimentation, observation, modeling

-analysis & communication

What is life

1. Energy processing: 

2. Regulation

3. Response to the environment

4. Growth & development 

5. Order

6. Evolutionary adaptation

Taxonomy

• The branch of biology concerned with naming & classifying specific

• Different levels of classification, each more comprehensive than those below it 

Homeostasis

•  the process by which a cell/organism maintains internal conditions w/in certain boundaries

Order of Taxonomy (from biggest to smallest)

-domain

-kingdom

-phylum

-class

-order

-family

-genus

-species

Currently recognized domains

Bacteria, Archaea, Eukarya

Currently recognized kindoms

Archaea, Bacteria, Protista, Fungi, Plantae, or Animalia

theory of evolution

-provides a framework for understanding how the diversity of life on Earth arose

3 observations abt life

1. Organisms are well suited (adapted) for life in their environments

• Environment includes both biotic & abiotic components 

2. Life shares many unifying characteristics 

3. Life is incredibly diverse

Aristotle

• Created Scala Naturae, proposed that species are organized into a sequence based on increased size & complexity-humans at the top 

evolution

descent with modification

James Hutton

• Proposed that Earth’s geologic features could be explained by gradual mechanisms, such as valleys being formed by rivers

Thomas Malthus

• Wrote an essay on the principle of populations -populations grow exponentially while resources grow linearly 

• Intraspecies competition/control (hunger, disease etc) to keep maintain population

Jean-Baptiste Lamarck

• Hypothesized that species evolve through use & disuse of body parts & the inheritance of acquired characteristics → later disproved by genetics

George Cuvier

• often credited as being the founding figure in paleontology

• Digging rock layer deeper → fossil older

Charles Lyell

• Used this thinking in his proposal that the same geologic processes are operating today as in the past, & at the same rate

Adaptations

 characteristics of organisms that enhance their survival & reproduction in specific environments 

6 observations of natural selection

-Species tend to produce more offspring than in necessary to replace the parents & maintain the population

-despite the huge # of offspring, adult populations of species stay fairly constant

-natural resources are limited & limiting

-Individuals in a population vary

-Much of that variation is heritable → offspring get their features from their parents

-Humans use artificial selection to select for preferred, heritable traits 

3 inferences of natural selection

-there must be a struggle for existence in nature w/ too many individuals & not enough resources

-the struggle for existence is not random, but selective (Survival of fittest)

-populations changer over time as the frequency of advantageous traits increases

3 main tenets of Natural Selection

1. individuals w/ certain heritable traits survive & reproduce at a higher rate than other individuals

2. Natural selection increases the frequency of adaptations that are favorable in an environment

3. if the environment changes, natural selection may drive adaptation to new conditions, giving rise to new species

Natural selection

-variation within the population

-variation must be heritable

must be diffs in reproductive success based on those diffs

Artificial selection

-variation within the population

-variation must be heritable

-diffs in reproductive sucess based on favorable heritable traits selected by humans

4 Evidence for evolution

1. anatomical & molecular homologies

2. fossil record

3. biogeography

4. experimental evidence - direct observations

homology

 similarities resulting from common ancestry

vestigial structures

•  remnants of features that served a function in the organisms’ ancestors 

Convergrent evolution

• the evolution of similar/analogous, features in distantly related groups

analogous traits

arise when groups independently adapt to similar environments in similar ways

microevolution

•  evolution on its finest scale; a change of allele freq win a population over time 

Microevolution can result from

○ Natural Selection

○ Sexual Selection

○ Genetic Drift

○ Gene flow

○ Mutation

macroevolution

• results in the formation or new species/ large groups of living things 

Describe how genetic variation arises and explain why it is a prerequisite for evolution

Genetic variation arises through mutation that creates new alleles

It is a prerequisite for evolution b/c natural selection can only act on variation with a genetic component.

gene

• unit of heredity

allele

form of a gene

genotype

• combination of alleles

homozygote

• possessing 2 of the same allele

heterozygote

• possessing diff alleles

dominance

•  1 allele masking the other in the heterozygous condition

phenotype

• an  organism’s appearance; observable traits or characteristics of an organism

Mutation

a change in the nucleotide seq of an organism’s DNA

Asexual reproduction

• Reproduction w/out fusion of gametes

• Based on mitosis

• 1 parent

• Results in offspring that are genetically identical to their parent

Sexual reproduction

• Reproduction involving fusion of gametes

• Based on meiosis

• 2 parents

• Results in offspring that are genetically diff each other & their parents

Sexual reproduction increases genetic diversity in 3 ways

1. independent assortment

2. crossing over

3. random fertilization

species

•  a group of individuals that are capable, through reproduction, of sharing alleles w/ one another

population

•  a localized group of interbreeding individuals

gene pool

•  all the alleles present in all the individuals in population

allele frequency

•  how common is that allele is in the population

Hardy-Weinberg Principle (5 conditions)

1. No mutations

2. Random mating

3. No natural selection

4. Extremely large population size

5. No gene flow

fecundity

The contribution an individual makes to the gene pool of the next generation relative to that of other individuals in the population

directional

• average phenotype of the population is changed in one direction → favors one extreme

disruptive

eliminates phenotypes near the average value → favors both extremes

stabilizing

• selection reduces both extremes in a population

sexual selection

 form of natural selection that can affect the freq of alleles in a gene pool

sexual dimorphism

• a diffs in secondary sexual characteristics between males & females

intrasexual selection

• direct competition among individuals of one sex (often males) for mates of the opposite sex

intersexual selection

• when indiviauals of one sex (usually females) are choosy in seletcing their mates

genetic drift

causes allele freq to change randomly → In some cases, drift can cause alleles that decrease fitness to increase in freq 

founder effect

•  a chance in allele freq that occurs when a new population is established 

bottleneck effect

•  a sudden reduction in the # of alleles present in a population

gene flow

The movement of alleles into or out of a population due to the movement of fertile individuals or their gametes.