FoB John Logsdon version

Scientific theories are often comprised of two components

Pattern and process

Pattern

observations about natural world

Process

mechanism that produces that pattern

Greek philosopher Plato claimed:

-Every organism was an example of a perfect essence,

or type, created by God

– Types were essentially unchanging

Typological thinking

a cognitive approach that classifies objects or organisms into distinct, fixed categories (types) based on shared characteristics, often ignoring individual variation

Aristotle organized typological thinking into linear scheme called ___

the great chain of being (scale of nature)

the great chain of being (scale of nature)

– Species were fixed types

– Species were organized into a sequence based on

increasing size and complexity

– Sequence started with minerals and lower plants

– Humans at the top (surpassed only

by angels and God)

Jean-Baptiste de Lamarck proposed formal theory of evolution

– Simple organisms originate at base of chain by

spontaneous generation (pattern of Lamarck’s theory)

– Organisms evolve by moving up in chain over time

– Lamarckian evolution is progressive, producing larger,

more complex or “better” species over time

Lamarck suggested process responsible for this pattern was:

inheritance of acquired characters

inheritance of acquired characters

– As individuals develop, their phenotype changes in

response to environmental challenges

– Phenotypic changes are passed on to offspring

Example of “inheritance of acquired charcaters”

Giraffes develop long necks from stretching to reach food and produce offspring with long necks

Charles Darwin wrote

Origin of Species

Charles Darwin’s evolutionary beliefts

Species change over time

•Divergent species share a common ancestor

•The mechanism that produces the change is

natural selection

Charles Darwin and _____ essentially co-discovered that the force of natural selection shapes the evolution of species

Alfred Russell Wallace

Core principles of evolution proposed by Darwin

Common ancestry and natural selection

Common ancestry

all current organisms are connected by descent through a series of organisms existing in the past

Natural selection

reproduction & survival is determined by characteristics of an organism in relation to the environment

Darwin described evolution as ____

descent with modification

____ are traces of organisms that lived in the past

Fossils

____ rocks are telling of previous species in the past

Sedimentary

____ are determined by comparison among the layers

Relative dates

____ are determined by tree rings, radiometric dating, and paleomagnetic

Absolute dates

Methods used for assigning absolute ages to relative ages

– Use radioactive decay (e.g. C14 vs. C12; “Carbon dating”)

-Radiometric dating:

Radiometric dating

– Based on observed decay rates (half-life of C14 =5730 yrs)

– Ratio of atoms in particular rock/fossil/sediment samples

Darwin interpreted extinction as evidence that

– Species are dynamic

– All species living on Earth have changed through time

Recent analyses of fossil record suggest:

– Over 99% of all species that have ever lived are now

extinct

– Extinctions have occurred continuously throughout

Earth’s history

law of succession

Early scientists observed that fossil species are strikingly similar to living species in the same geographic areas

Tiktaalik

Represent an intermediate between “normal” fish and tetrapods

Vestigial trait

– A reduced or incompletely developed structure in an organism that has no (or reduced) function

– Clearly similar to functioning organs or structures in closely related species

Examples of vestigial traits

– Some whales and snakes have tiny hip and leg bones that do not help them swim or slither

– Ostriches and kiwis have reduced wings and cannot fly

– Blind cave-dwelling fish have eye sockets but no eyes

– Monkeys & other primates have long tails, and we don’t

Examples of modern evolutionary changes

– Evolution of antibiotic resistance in bacteria

– Evolution of beak shape in finches

Homology

Similarity due to descent from common ancestor

Homology is recognized & studied at three interacting levels

1. Genetic

2. Developmental

3. Structural

Genetic homology

the existence of shared ancestry between pairs of genes or DNA sequences in different species, reflecting descent from a common ancestor

Genetic code—the most fundamental homology:

All organisms use the same rules for transferring information coded in DNA into proteins. (w/ minor exceptions)

Developmental homology

similarities in the embryonic development, structural origins, and developmental processes of different organisms, indicating shared ancestry

Structural homology

physical features or anatomical structures in different species that share a common evolutionary ancestor, even if their functions now differ

Speciation

the evolutionary process by which populations evolve to become distinct species, forming new, reproductively isolated lineages

Internal consistency

Observation that data from independent sources agree in supporting predictions made by a theory

Descent with modification

– More successful and powerful scientific theory

– Explains observations that special creation does not

Example of internal consistency

cetaceans

Artificial selection

the human-driven process of breeding plants or animals to enhance desirable traits, such as increased agricultural yield, specific pet behaviors, or aesthetic features

The “struggle for existence”

Many more individuals are born than can survive

Thus, people compete for resources

Evolution by natural selection occurs when:

1) Heritable variation leads to

2) Differential reproductive success

Fitness

Ability of an individual to produce surviving, fertile offspring relative to that ability in other individuals in population

Adaptation noun

Heritable trait that increases an individual’s fitness in particular environment relative to individuals lacking that trait

Adaptation verb

Process by which such traits increase in populations

Selection

Differential reproduction as result of heritable variation

DNA from rifampin-resistant bacteria was found to have____

single point mutation in gene called rpoB

Alleles That Confer Drug Resistance Increase in_____

Frequency When Drugs Are Used

____don’t evolve;____ do

Individuals; populations

Natural experiments

allow researchers to compare treatment groups created by an unplanned change in conditions

polygenic

characteristics, such as height, skin color, or disease risk, influenced by two or more genes rather than a single gene

Individuals simply produce ____ surviving offspring than other individuals do

more

Mycoplasma tuberculosis

is the bacteria causing tuberculosis (TB), a severe infectious disease affecting the lungs and other organs

Acclimatization

occurs when individual’s phenotype changes in response to changes in environment

Adaptation occurs when…

allele frequencies in a population change in response to natural selection

Evolution is not ____ and it does not produce “better”or more complex organisms

progressive

Fitness trade-off

an evolutionary concept where an increase in one advantageous trait results in a decrease in another, as organisms face limited resources

Genetic correlation

measures the extent to which the same genes influence two different traits, indicating shared genetic, rather than environmental, factors

pleiotropy

a genetic phenomenon where a single gene influences multiple, seemingly unrelated phenotypic traits

Abiotic

the non-living, physical, and chemical components of an ecosystem

Evolution vs Natural selection

Evolution: change through time

Natural selection: one process that causes adaptive evolution

Hardy-Weinberg equilibrium

a principle stating that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences, such as selection, mutation, migration, or genetic drift

gene pool

is the sum of all copies of all alleles at all loci in a population

p + q =

1

What are p and q?

Two different alleles of the same gene

When there are 2 alleles, how many possible genotypes are there?

3

Hardy–Weinberg equation

p²+2pq+q²=1

allele frequency

polymorphic

the occurrence of two or more clearly different forms (morphs or phenotypes) within the same population of a species

If there is only one allele at a locus, its frequency = 1

The population is monomorphic at that locus; the allele is said to be fixed

Hardy–Weinberg principle

predicts the genotype

frequencies and allele frequencies in the next generation: Allele and genotype frequencies do not change

Random mating

no mate choice; gametes combine randomly

No natural selection

all individuals contribute equally to gene pool

No genetic drift (random allele frequency changes)

alleles are not picked by chance because population is not large

No gene flow

no new alleles added or lost from\gene pool by migration

Inbreeding

Nonrandom mating between relatives

genetic drift

causes allele frequencies to change randomly

gene flow

occurs when individuals leave one population, join another, and breed

Mutation

modifies allele frequencies by continually introducing new alleles

Self-fertilization is the ___

Most extreme form of inbreeding

Self-fertilization example:

Many flowering plants contain both sperm-producing and egg-producing organs and self-pollinate

Homozygous parents that self-fertilize produce ___

all homozygous offspring

Heterozygous parents that self-fertilize produce

homozygous & heterozygous offspring (1:2:1 ratio)

Inbreeding in general increases ____ and decreases ___

frequency of homozygotes; Reduces frequency of heterozygotes

Why doesn’t inbreeding cause evolution?

Allele frequencies do not change in population as a whole

Inbreeding, while not directly influencing evolution, can affect evolution by___

increasing the rate at which natural selection eliminates recessive deleterious alleles (that lower fitness) from a population

inbreeding depression

the reduction in fitness, survival, and reproductive success of offspring resulting from mating between closely related individuals

Sexual selection

An organism actively chooses a certain mate based on physical and/or behavioral traits (another form of nonrandom mating)

Sexual selection is different from inbreeding because____

It leads to changes in allele frequencies in population

Sexual selection is a form of ___

natural selection

Sexual selection may favor traits that ___ an individual’s chances of reproduction but ___ its chances of survival

enhance; reduce

Heritable variation

differences in traits among individuals within a population that are passed down from parents to offspring via genetic information

Selection can occur only if ___ variation exists in population

heritable

___ variation can make populations less able to respond successfully to changes in the environment

Lack of

If environmental change is severe, population may become ___

extinct

Stabilizing selection

a type of natural selection that favors average, intermediate phenotypes rather than extreme variations, reducing genetic diversity and maintaining the status quo

Directional selection

a type of natural selection that favors one extreme phenotype over others, causing the allele frequency to shift over time in that direction

Disruptive selection

a type of natural selection that favors extreme phenotypes over intermediate ones, increasing genetic and phenotypic diversity