BIO 106 Exam #1

What are the components of the Theology of Special Creationism?

Fixity of species and fixity of earth

Fixity of species

• Species are fixed and unchanging

• Species seen today are the same as when created

• Species specially created for specific habitats

Fixity of Earth

• Age of Earth = 6000 years old

• Landscapes are the same today as when they were created

Aristotle - Scala Naturae

• Species are fixed

• Perceived a pattern - a hierarchy of increasing complexity

• Each perfectly formed for its place on the “scale of nature”

Linneaus prevailing idea before Darwin

Instead of a linear hierarchy, saw patterns suggesting species could be clustered into nested categories

Jean-Baptiste de Lamarck (1809) influence on Darwin’s thinking

• Species can change over time

• Traits change based on use and disuse

• Inheritance of acquired characteristics

Charles Lyell (1830) influence on Darwin’s thinking

• Geologist who argued the Earth is very old

• Claimed Earth is not fixed - it has changed gradually over time

• The accumulation of small, gradual changes add up big scale changes to Earth’s landscape

Darwin’s journey

• Sailed on HMS Beagle as the ship Naturalist

• Started journey believing species were specially created

• That worldview came into questions as he saw things that did not fit

• He saw things that shook his certainty that Special Creationism was true

What is special creationism: Earth is young (6000 years old)?

• Lyell argued landforms formed over long periods of time (millions of years) ex. mountains and rivers carved valleys

• Darwin discovered fossil sea shells at 10,000 feet in the Andes

Galapagos Island Archipelago

Found endemic (unique to that place) species on the geologically young islands

• Unique but with shared characteristics to those on nearest mainland

Darwins first hypothesis

The Galapagos were populated by species migrating form the nearest mainland instead of having been specially created for these island habitats

Explained:

• No amphibians, no terrestrial mammals (unable to survive the trip)

• Many birds and reptiles (they have the ability to make it and colonize)

The problem of endemic species

If they don’t occur on mainland, they cannot have migrated tot he islands

Darwin’s conclusion on endemic species

Island species are the descendants of colonizers who came from the mainland, BUT they are different because they have changed over many generations in ways that make them better adapted to the harsh environment of the islands

Theory of Evolution: descent with modification

• Populations can accumulate modifications from generation to generation

• Small changed accumulate resulting in big differences

• This accumulation of changes can lead populations to become significantly different from their ancestors

• A sub-population can split into two, each following a different trajectory

• Species are RELATED to each other by shared lineages (family tree)

• Creationism says each species created INDIVIDUALLY - so not related by ancestry

How do species change?

Natural selection

A heritable trait is one that

Is determined at least in part by genes passed from parents to offspring

What does it mean that organisms have a nearly universal genetic code?

A specific DNA sequence encodes the same information in one species as it would in nearly any other

An adaptation is _____.

A trait that gives an organism a reproductive advantage in the current environment

What lead to Darwin’s major inferences?

• Members of a population vary in their heritable traits

• Although organisms can produce huge numbers of offspring, many of these do not survive and reproduce

What is the meaning of Darwin’s expression “decent with modification”?

Evolutionary change over time

Varieties of staphylococcus aureus that are resistant to the drug methicillin _______.

• Already existed in the population before methicillin was developed

• Don’t have and advantage in the absence of methicillin

• Were strongly selected for as methicillin became widely used to that bacterial infection

A challenge yo traditional (pre 1980) ideas about species came from embryology, when it was discovered that ______.

Embryos of dissimilar organisms, such as sharks and humans, show more similarities than appear in adult forms

Example of pair of homologous structures

Maple leaf and oak leaf

The theory of evolution through natural selection is considered a scientific theory because _____.

• It is general enough to provide many testable hypotheses

• It is broad enough to scope to explain many observations

• It is supported by a massive body of evidence from many disciplines

What was Darwin’s mechanism for change?

Natural selection

3 components of the engine of natural selection

1. Genetic variation between individuals in a population (some have more adaptive traits than others)

2. Selective pressure (selects some variants over others. Individuals are not active participants-selection happens to them)

3. Reproduction (favorable traits passed to offspring)

A harsh environment acts as a selective pressure

Those individuals with better combination of traits will ultimately have more offspring; so next generation is skewed towards enhanced adaptation

Competition for resources acts as a selective pressure (creates a struggle for existence because of scarce resources)

Results in differential reproductive success; those individuals with better combination of traits will ultimately have more offspring; so next generation is skewed towards enhanced adaptation

What is artificial selection?

Selectively breed to push populations toward favorable trait combinations

How does artificial selection work?

• Variation must exist in population

• Breeder decides which traits are favored

• Individuals with favored traits are bred together, leaving behind unfavorable traits

Example of artificial selection: selective breeding of wolves →

Many breeds of dogs

Bacterial Resistance to Antibiotics: if some bacteria happen to have an allele that can detoxify an antibiotic…

If the antibiotic is added to the environment, it will kill those without the allele

• Individuals with the allele will survive and reproduce

• Next generation has more bacteria with the resistance allele

Selective agent

Decides which individuals survive and reproduce, and which do not survive

Natural selection =

Mechanism for change

Selection acts on _________ in a given population

Differences between individuals

The environment and community acts as the ________

Selective agent

The original source of al genetic variation is _____

Mutation

What is the causes of evolutionary change?

• Gene flow

• Mutation

• Natural selection

• Genetic drift

Generation to generation change in the allele frequencies in a population is _____

Microevolution

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population?

Founder effect

Natural selection changes allele frequencies because some _____ survive and reproduce than others.

Individuals

What is the only evolutionary mechanism that consistently leads to adaptive evolution?

Natural selection

In evolutionary terms, an organism’s relative fitness is measured by its ________

Contribution to the gene pool of the next generation

What type of selection tends to increase genetic variation?

Disruptive selection

What does the x-axis represent?

The value of a particular characteristic; characteristics of an organism can include such traits as size and color

What kind of selection appears to have made giraffes the long-necked animals?

Directional selection

Which kind of selection is most likely regarding the both weight of babies?

Stabilizing selection

What kind of selection acts on beak size in seedcrackers?

Disruptive selection

How is the process of evolution revealed by the imperfections of living organisms?

• Organisms inherit a basic form from their ancestors, and the form is modified by natural selection over time

• Imperfections in an organism result from a variety of other constraints, such as lack of genetic variation for the trait

Traits under genetic control are passed from parent to ____

Offspring

Traits are encoded in DNA molecules

Chromosomes

Sequences of nucleotides that code for a protein =

Genes

Genes can suffer mutations which are

Changes in the sequence

Variations of a gene are called ____

Alleles

New variations come from _____

Mutation

Heritable traits =

Genetically-based traits

What happens when a random change to the DNA happens

It can alter the trait for better or worse

What are mutations triggered by?

DNA replication, UV light, chemical exposure, etc.

Because most organisms are the result of generations of natural selection, mutations tend to be _____ more often than _______.

Harmful; beneficial

Harmful alleles can persist if they are ______

Recessive; these are not expressed in parents and passed to offspring

What does sexual reproduction create?

New combinations

Natural selection operates on the suite of traits expressed by individuals not……

Just one trait at a time

A gene pool is all the different alleles of all the different genes in a ______

Population

Population also reflect the relative _____ of the different alleles

Frequencies

What does it mean for an allele to be “fixed” in a gene pool?

When only one allele exists for a given gene and there is no variation

If nothing acts to cause allele frequencies to change from generation to generation……

Then the population is not evolving

Populations not evolving are in _______

Hardy-Weinberg Equilibrium

What are the conditions for Hardy-Weinberg equilibrium?

1. No natural selection

2. No mutation

3. Random mating

4. No gene flow

5. Extremely large population size (no genetic drift)

Mutation

Source of new alleles

Non-random mating

Does not alter allele frequency but affects distribution of alleles in individuals

Gene flow

Alleles from other populations

Genetic drift

Random chance can affect allele frequencies

Natural selection

Alleles that code for beneficial traits are selected for - frequencies go up

• This is the only form of evolution that is adaptive

Non-random mating

Skews towards extremes

Change in allele frequencies due to ______

Random chance

Is the effect of genetic drift more pronounced in small or large populations?

Small

What is NOT a possible outcome of genetic drift?

The population slowly becomes better adapted for its environment

What is the Bottleneck effect?

When a population is sharply reduced in size

When genetic diversity is severely reduced…..

• Results in the loss of some alleles (including beneficial ones)

• Fixation of other alleles

What is the Founder effect?

A few individuals start a new population

• New population has different allele profile due to random nature of migration event

• New population may be missing some alleles or shows a fixation for other alleles

What is gene flow?

Alleles introduced from other populations by migration will affect gene pool of both populations

• Can introduce new alleles (or lose them)

• Can alter allele frequencies

What make natural selection a different sort of agent of change in a population?

It is the only one that leads adaptation

Natural selection is only mechanism resulting in _____ evolution

Adaptive

Evolution is a product of _____ and _______

Chance; sorting

_______ is from mutation, genetic drift and other mechanisms

Chance

________ is from favoring of certain alleles over other by natural selection

Sorting

• This is non-random; adaptive

• Frequencies of beneficial alleles are continuously increasing

Who experience selection?

Individuals

What evolves?

Populations (individuals do not evolve)