Name ______Period ______

Evolution Notes

Evolution

What is a Theory versus a Hypothesis?

Hypothesis

Theory

Origins of Evolutionary Thought

  1. 1785 - James Hutton: Proposed earth is shaped by geological forces taking place over extremely long periods of time. Estimates Earth to be millions – not thousands – of years old.
  2. 1798 – Thomas Malthus: Predicts that the human population will grow faster than the space and food supplies needed to sustain it.
  1. 1809 – Jean-Baptiste Lamarck: Proposed the inheritance of acquired traits. His ideas are wrong, but he is still one of first to propose a new mechanism of how organisms change over time.
  2. 1833 – Charles Lyell: Explained that processes occurring now have shaped Earth’s geological features over long periods of time.

Charles Darwin

Variation -

Adaptations -

Some of Darwin’s Most Important Insight to Natural Selection

Darwin noticed lots of variation of species in nature & on farms.

  • This was due toArtificial selection –
  • After all his studies in theGalápagos Islandswhat was Darwin’s proposed mechanism called? ______

Darwin’s Conclusions

Evolution Occurs by Natural Selection

  1. ______
  • Competition among members of a species exist for food, living space, and the other necessities of life.
  • Survival of the Fittest– Individuals that are better suited to their environment – that it, with adaptations that enable fitness – survive and reproduce more successfully; Darwin referred to this as natural selection

Fitness–

  1. Adaptation
  • Certain variations allow individuals to adapt and survive better in their environment. Those more successful will live longer and share those adaptations to future generations.
  • Natural Section cannot be seen ______- only observed as changes in a ______over many generations.
  1. Descent with Modification
  • Each
  1. Variation
  • Many genes have at least two genes or alleles.

Evidence of Evolution
comes primarily from these sources….

  1. Fossil record
  2. Geographical distribution of living species
  3. Structural similarities of related life forms
  4. Chemical similarities in DNA
  5. Embryology

1. Evidence of Evolution: Fossil Record

Age of Fossils

Relative Dating

In relative dating, the age of a fossil is determined
by comparing its ______with that of
fossils in other layers of rock.

Paleontologists estimate the age

Radioactive Dating

Scientists use radioactive decay to assign ______ages to rocks.

Radioactive elements decay, or break down, into nonradioactive elements at a steady rate, which is measured in a unit called a half-life.

A half-life is the length of time required for half of the radioactive atoms in a sample to ______.

2. Evidence of Evolution: The Geographical Distribution of Living Species

  • Similar, but unrelated species exist. Similar animals in different locations were the product of different______of evolutionary descent.

3. Evidence of Evolution: Structural Similarities of Living Things

i. Homologous Structures ii. Vestigial Structures iii. Analogous Structures

(i)Homologous Structures of Living Organisms

Examples:

Homologous Structures - Structures that have
different mature forms in different organisms but
develop from the ______embryonic tissues.

Same development – different
______.

Provide strong evidence that all four-limbed
vertebrates have descended, with
modifications, from ______
ancestors.

(ii) Vestigial Organs

Vestigial Organs – Organ that serves no useful ______in an organism; Traces of ______structures.

Examples:

(iii) Analogous Structures

Analogous Structures - Structures that evolve separately to perform a ______function.

Different development – same ______.

Provides evidence for ______evolution because they have very similar structures even though they were completely independently derived to fill a similar purpose.

Examples:

4. Evidence of Evolution: Chemical Similarities

Despite the great diversity of life on our planet, the simple language of the DNA code is the ______for all living things.

Amino Acid Comparison

The more closely related two species are, the more amino acid sequence ______should be seen.

5. Evidence of Evolution: Similarities in Embryology

The early stages, or embryos, of many animals with backbones
are very ______.

EVOLUTION OF POPULATIONS

Variation increases chance of survival

Genetic variation is studied in ______.

A ______is a group of individuals of the same species that interbreed.

Gene Pool– consists of ______, including all the different alleles, that are present in a population.

Sources of Genetic Variation

The two main sources of genetic variation are:

1.Mutations – Any ______in a sequence of DNA.

Can occur because of ______in the replication of DNA or as a result of radiation or chemicals in the environment.

2. Recombination - The natural formation in offspring of genetic ______not

present in parents.

Independent assortment occurs during the production of ______– each homologous pair moves independently during meiosis.

Crossing over during meiosis further increases ______.

Natural Selection acts of Distribution of Traits

Natural selection can affect the distributions of phenotypes in any of three ways:

  1. Directional Selection 2. Stabilizing Selection 3. Disruptive Selection

1. Directional Selection

Directional Selection – Takes place when individuals at ______of the curve have higherfitness than individuals in the middle or at the other end.

Sketch an example:

2. Stabilizing Selection

Stabilizing Selection – Takes place when individuals near the ______of the curve
have higher fitness than individuals at either end of the curve.

Sketch an example:

3. Disruptive Selection

Disruptive Selection– Takes place when individuals at the ______and ______ends of the curve have higher fitness than individuals near the middle.

Sketch an example:

Other Mechanisms for Evolution besides natural selection

  • ______- the movement of alleles (genes) from one population to another.

Affected by:

1. 2. 3.

Genetic Drift

Genetic Drift–Random change in allele frequencies that occurs in small populations due to ______.

Unlike natural selection because:

It happens by ______- caused by big event live overhunting or a natural disaster (fire, landslide or lightning strike).

Doesn’t work to produce ______like natural selection does.

How Does Genetic Drift Occur?

In each generation, some individuals may, just by chance, leave behind a few more descendants (and genes, of course) than other individuals. The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better” individuals. It happens to all populations – there’s no avoiding the vagaries of chance.

Evolution vs. Genetic Equilibrium

Are there any conditions under which evolution will not occur?

Hardy-Weinberg Principle

Hardy Weinberg Equation: p2 + 2pq + q2 = 1

p + q = 1

Five conditions are required to maintain genetic equilibrium from generation to generation:

  1. There must be random mating.
  2. The population must be very large.
  3. There can be no movement into or out of the population.
  4. There can be no mutations.
  5. There can be no natural selection.

The Hardy-Weinberg Equation

The Process of Speciation

Speciation – formation of a new species (Group of organisms that breed with one another and produce ______offspring)

Speciation & Reproductive Isolation

The gene pools of two populations must become ______for them to become new species.

As new species evolve, populations become reproductively isolated from each other.

Reproductive Isolation - When the members of two populations ______interbreed and produce fertile offspring.

Reproductive Isolation

Reproductive isolation can occur in a variety of ways, including:

  1. Behavioral Isolation
  2. Geographic Isolation
  3. Temporal Isolation

1.Behavioral Isolation

Example: mating courtship songs of Eastern and Western Meadowlarks

2. Geographic Isolation

Example: The Abert & Kaibab Squirrelseperated with Colorado River

3. Temporal Isolation

Example: Orchids in rainforest polinating on seperate days

Patterns of Evolution

Some large-scale evolutionary patterns and processes that occur over ______periods of time are:

  1. Extinction4. Gradualism
  2. Convergent Evolution5. Punctuated Equilibrium
  3. Divergent Evolution6. Coevolution

(1.) Extinction

When does an animal go extinct: Most likely when: ______but also when ______.

(2.) Convergent Evolution

Convergent Evolution – Process by which unrelated organisms come to

______oneanother.

(3.) Divergent Evolution

Divergent Evolution – The process of two or more related species becoming more
and more ______.

(4.) & (5.) Gradualism vs. Punctuated Equilibrium

How quickly does evolution occur?

Gradualism – Long time with ______change.

Punctuated Equilibrium - Long, stable periods interrupted by brief periods of more ______change.

  • Think about this…How did a tiger get its stripes? Gradually or with a huge, quick change?

Gradualism Punctuated Equilibrium

(6.) Coevolution -

Common Misconceptions

Humans did not come from monkeys. Instead, humans
and primates share a common ______.

Darwin is not the only evolutionary theorist. Darwin
utilized evidence from other evolutionists to draw
his ______.

Evolution does not happen quickly – it occurs over
______of time.

Change does not occur at the individual level – it occurs in
______.

Cladogram

Cladogram– Diagram that shows the evolutionary relationships among a group of organisms.

Is constructed using derived characters, which are characteristics that appear in recent parts of a lineage but not in older members.

Phylogeny- Study of evolutionary relationships among organisms.

Biologists now group
organisms into categories
that represent lines of
evolutionary descent, or
phylogeny, not just physical
similarities.