Bio - NATURAL SELECTION, EVIDENCE FOR EVOLUTION, and CLASSIFICATION

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Charles Darwin

English naturalist who studied the environment and formulated a theory of evolution by natural selection

In Darwin's travels to the Galapagos Islands, he noticed

that there was a lot of different species on the islands

Many of the organisms found on the islands were __________ to each other, but (not exactly, exactly) alike

similar, not exactly

Where were the organisms that were similar to the ones on the Galapagos Islands found?

South America

Where did Darwin think the plant and animal species from the Galapagos Islands had come from?

the mainland of South America

What did Darwin think caused the changes from the original species to the ones on the Galapagos Islands?

He believed that these island organisms faced different conditions than from those on the mainland

List some conditions they could have faced on the Galapagos Islands that caused the finches to change

different weather, predators, prey, resources

Darwin thought that species slowly changed over many ________________ to become _________ adapted in the new conditions gradual change over time

generations, better

Darwin's explanation for how evolution could occur in nature

NATURAL SELECTION

Natural selection

the process by which individuals that are better adapted to live in their environment are more likely to survive and reproduce

The organisms with the good differences can give the (unhelpful/helpful) adaptations to their babies

helpful

Darwin believed that the helpful traits would (decrease/increase) while the (helpful/unhelpful) traits would disappear!

increase, unhelpful

Which moth do you think will survive?

Two moths on a light tree. One is white and one is black.

light moth

Different \__________________ will help a species survive in different habitats

adaptations

How did Darwin's Finches adapt to the Galapagos Islands?

* Different parts of the island have different resources
* Depending on what resource is available in their habitat, the finch population has developed a different beak over many generations
* For example, if there are more insects available on one part of the island, the finches that have beaks suited for insect eating will survive and reproduce, so most of the finch population there will have those successful beaks

Darwin's Theory of Natural Selection can sometimes be called \__________________

"Survival of the Fittest"

An organism's fitness

its ability to survive and reproduce

adaptation

A HELPFUL trait that helps an organism survive and reproduce

Examples of adaptations

camouflage, shells, mimicry, long neck, sharp teeth, etc.

an adaptation (helpful) trait will \____________ an organism's fitness

increase

natural selection can happen only if the five following conditions are met

1. A population of organisms has variations.

* There are different genes and traits in the population.


2. Some variations are favorable.

* Some genes and traits are better than others


3. More offspring are produced than survive
4. Those that have the favorable traits will survive and pass down the favorable trait to their offspring
5. There will be more organisms in the population that have the favorable trait, therefore the population changes over time.

Because of ___*____ the traits that are present in a species will change over time, depending on which trait will help them _______*__ and __________.

natural selection, survive, reproduce

The \___________ adaptations will increase in the species, and the non-helpful adaptations will \_______________

helpful, decrease

Stabilizing selection

eliminates the extreme ends of a trait and favors the average version of a trait

example of stabilizing selection

Human babies who are born with below-normal and above-normal weights have lower chances of survival than babies born with average weights. Therefore, most babies born have an average birth weight.

Directional Selection

When ONE extreme version of a trait is more fit and selected for (compared to the average version)

example of directional selection

If only large seeds were available, birds with larger beaks could eat while the birds with small beaks will have a harder time eating. The birds with larger beaks would be more successful in surviving and passing on genes.

Disruptive Selection

The "average" phenotype is eliminated and both extremes are left

example of disruptive selection

Tail length - short tails help keep predators from catching them, long tails are good for balance in trees, medium tails don't help

Artificial Selection

people choosing which traits they liked and breeding those organisms

selective breeding is another name for

Artificial Selection

\________________ breeding, helped Darwin come to the conclusion that species could change over time

selective

How did selective breeding help Darwin come to the conclusion that species could change over time?

He thought that a process similar to artificial selection might occur in nature without the help of humans.

Sexual Selection

when individuals select mates based on heritable traits

example of sexual selection

Peacock Feathers - Male peacocks have long colorful feathers to attract mates while females don't have that

Example of an Adaptation for Survival

Mimicry

mimicry

one species evolves to resemble another species

How is a harmless species mimicking a harmful species helpful?

causes predators to avoid them because they can't tell the difference

5 types pieces of Evidence for Evolution

The Fossil Record, Similar Anatomy, Similar Embryology, Similar Molecular Biology (DNA), and Biogeography: Location of Species

fossils

a record of the history of Earth

By comparing fossils from older rocks with fossils from younger rocks, scientists can see

life has changed over time

Homologous Structures

Structures that are similar and are inherited from a common ancestor but have different functions

example of Homologous Structures

The forelimb of different organisms are adapted for different uses, but they all have similar bones

Vestigial Structures

body parts left behind that HAD important functions in common ancestors but are now useless

Example of vestigial structure

The appendix is a structure important in digestion in most mammals, but has no use in humans

Analogous Structures

Structures that have the same function but are NOT inherited from a common ancestor

Example of analogous structures

The wings of a bat and the wings of a dragonfly

How does an analogous structure provide evidence for evolution?

This shows that similar features can evolve separately in a similar environment

What did scientists observe when looking at how different organisms develop (specifically as embryos)?

they noticed that most animals begin their lives looking very similar as growing embryos

What does Similar Embryology suggest?

This suggests that all of them evolved from a shared ancestor!

What did scientists notice when comparing DNA and amino acid sequences of different organisms?

there were many similar sequences between organisms

Similar Molecular Biology suggests

all organisms evolved from a common ancestor

The geographic distribution of species and the fossils found in certain locations suggested that

organisms evolved from common ancestors

examples of Biogeography as a piece of evidence for evolution

Fossils of a particular ancient reptile are found on multiple continents! This was due to their potential connection when Earth contained a super continent.

Species

A group of organisms that share common features/characteristics and can interbreed with one another and produce fertile offspring.

Speciation

the process where some organisms of the same species change so much that they can no longer reproduce together, and so they become a separate species over time

Allopatric Speciation

Allopatric speciation is when a geographical barrier divides a population into 2 or more physically separated populations

How does Allopatric Speciation make a new species?

After enough time, the separated species will evolve so much that they can no longer interbreed which makes them a separate species!

Sympatric Speciation

A species evolves into two separate species without a physical barrier

How does Sympatric Speciation result in a new species?

usually due to sexual selection, which leads to reproductive isolation —not being able to mate together again!

2 ways that organism populations are prevented from reproducing with one another

Prezygotic barriers and Postzygotic barriers

Postzygotic barriers

AFTER egg is fertilized

Prezygotic barriers

BEFORE an egg is fertilized

example of Prezygotic barriers

habitat isolation, temporal, mechanical, behavioral, gametic isolation

Ex. Eastern vs. Western Meadowlark have different mating song and don't interbreed (behavioral isolation)

example of Postzygotic barriers

reduced hybrid viability, reduced hybrid fertility, hybrid breakdown

Ex. A horse and a donkey are separate species because even though they can mate, the offspring—a mule - is sterile

How Are Species Related to One Another?

All organisms are related through descent from a remote common ancestor

The more recent their separation, the more recently they shared a \__________ \___________

common ancestor

Cladograms show

how organisms are related

Cladograms show how organisms are related, based on

shared common characteristics and most recent common ancestors

The ________ your branch is to another species on a cladogram, the more closely related you are and the (more/less) characteristics you share.

closer, less

Node (on a cladogram)

where two branches meet

What does a node represent?

common ancestor

There are traits listed on the cladogram. If you branch off \_______ that characteristic is listed, you HAVE that characteristic or trait.

AFTER

A cladogram is a made of \____________ (group of species that includes a single common ancestor and all descendants of that ancestor).

Clades

clade

a group of species that includes a single common ancestor and all descendants of that ancestor—living and extinct

Root of the tree (on cladogram) \= the \_____________

ancestors

Branches (on cladogram) \= the \________________ of that ancestor

descendants

As you move from the root to the tips, you are moving (backward/forward) in time.

forward

TAXONOMY

the science of naming and classifying organisms into groups

Biodiversity

the number of different species that are present in a certain area

Who came up with the system we use to organize organisms?

Carolus Linnaeus

Organisms are put in categories based on their \________ \___________ from very broad to very \____________.

characteristic similarities, specific

This system uses large groups divided into smaller groups (subgroups) called _____.

taxa

Taxonomic Categories

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Scientific Name (made up of)

genus and species

first word in scientific name

Genus

second word in scientific name

species

Scientific names are always \______________ or in italics

underlined

Why is Taxonomy Useful?

Helps stop confusion within scientists and to show how organisms are related.

cladograms show

evolutionary relationships among organisms, their common ancestors they branched from, as well as characteristics they have in common

The Three Domains

Bacteria, Archaea, Eukarya

Prokaryotes

simple organisms with NO nucleus in their cells

Prokaryotes contain the kingdoms of

archaebacteria and eubacteria

Eukaryotes

more complex organisms WITH A NUCLEUS and cell organelles

Eukarya contain which kingdoms

all except archaebacteria and eubacteria

The 6 Kingdoms

Archaebacteria, Eubacteria, Protista, Fungi, Plantae, Animalia

How are organisms placed into their kingdoms?

Cell type - complex or simple, Their ability to make food, The number of cells in their body

ARCHAEBACTERIA

Prokaryotic, Contain cell walls with NO peptidoglycan, Simple organisms (single celled), Contain autotrophs AND heterotrophs, Ancient bacteria, Found in extreme environments

EUBACTERIA

Prokaryotic, Contain cell walls made of peptidoglycan, Simple organisms (single-cell), Contains autotrophs AND heterotrophs, "Common bacteria" - most bacteria are in this kingdom, Found everywhere

PROTISTA

Eukaryotic, Contain cell walls made of cellulose, More complex (uni and multicellular), Contains both autotrophs and heterotrophs, Slime molds and algae are protists, Includes all microscopic organisms that are not in one of the other groups