AP Bio: 2.1 - Descent with Modification: A Darwinian View of Life

:D remember to do the study guide!

How do organisms evolve?

Organisms change over time through natural selection. (we’ll get to that later)

How did Charles Darwin come to his conclusion of evolution? What did he notice?

Charles Darwin noticed that some fossilized organisms no longer exist on the planet. He also noticed that fossils of organisms do not always resemble their modern-day descendants completely.

Who is Jean Baptiste Lamarck

Another scientist who had a theory about how organisms change over time. (it was wrong btw)

Jean Baptiste Lamarck wrote what book?

Theory of Evolution (1809)

Jean Baptiste Lamarck’s theory of Use and Disuse

The parts of the body that were used/needed most often would get stronger and bigger. (eg. A giraffe’s neck growing longer)

Jean Baptiste Lamarck’s theory of Inheritance of Acquired Characteristics

Modifications can be passed on from parent to child.

Jean Baptiste Lamarck’s importance?

He recognized that species evolve, even though his explanation was flawed.

Evolutionary change is based on…

Interactions between populations & their environment which results in adaptations (inherited characteristics) to increase fitness

Evolution (Darwin)

Descent with modification.

Evolution (normal def)

Change over time in the genetic composition of a population from generation to generation.

Natural Selection

Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals.

Natural selection increases the adaptation of organisms to their environment over time.

If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species.

Evolution by Natural Selection

1\.  Overproduction of offspring

2\.  Variation exists among offspring. 

3\.  Offspring struggle to survive (competition).

4\.  Survival of the fittest or the best adapted.

5\.  Best adapted reproduce and pass their genes to their offspring.

What is the source of the variation?

Sexual Reproduction (meiosis, crossing over, independent assortment and fertilization).

Mutations (random changes in nucleotide base sequences in DNA).

Did Darwin know about any of these sources of variation at the time?

Nope :D

What do the offspring compete for? (give examples)

They compete for food, mates, territory, shelter, hide from  predators.

Acquired characteristics **are or are not** passed to offspring?

Are not.

What did Darwin study to help lay the groundwork for his ideas.

Studying fossils.

What are fossils?

Remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata.

Charles Darwin (who is he??)

English naturalist.

What did Darwin do in 1831?

1831: joined the *HMS Beagle* for a 5-year research voyage around the world.

What did he do while on his research voyage?

Collected and studied plant and animal specimens, bones, fossils.

What was his most notable stop?

The Galapagos Islands.

Resistant bacteria (define)

Antibiotic resistant bacteria are bacteria that are not controlled or killed by antibiotics.

Random mutation (define)

A random mutation occurs when your set of DNA is changed by being replicated incorrectly.

What do random mutations create?

Genetic variation.

Susceptibility of bacteria (define)

Susceptibility is a term used when microbe such as bacteria and fungi are unable to grow in the presence of one or more antimicrobial drugs.

Effectiveness of antibiotic (define)

How well they are able to kill bacteria or prevent them from reproducing and spreading. 

Adaptation (define)

A change or the process of change by which an organism or species becomes better suited to its environment.

Antibiotic was the selecting factor (define)

The antibiotic was the selecting factor as to which bacteria were strongest/strong enough to survive and reproduce.

Pass on resistant genes to the next generation (define)

The bacteria that survive the antibiotic reproduce and pass on their resistant genes to the next generation of bacteria.

Do individuals evolve?

No. Populations evolve over time.

Natural selection can only ______ or _______ heritable traits that vary in a population

__increase__ or __decrease__

Adaptations in different environments?

They vary.

What did Darwin hypothesize while on the Galapagos Islands.

He hypothesized that species from South America had colonized the Galápagos and speciated on the islands.

In reassessing his observations, what did Darwin perceive?

Adaptation to the environment and the origin of new species as closely related processes

Artificial selection

Modifying other species by selecting and breeding individuals with desired traits. (like domestic animals → cats & dogs)

Natural selection does not only create new traits, but also…

edits or selects for traits already present in the population.

What determines which traits will be selected for or selected against?

The environment.

Evidence for Evolution

1. Fossils
2. Homologous Structures (similar anatomy)
3. Similar Biochemistry (similar DNA, RNA, & amino acid sequences)
4. Similar Embryo Development
5. Vestigial Structures

Homology

Similarity resulting from common ancestry.

Homologous structures

Anatomical resemblances that represent variations on a structural theme present in a common ancestor. (eg. the forelimbs of humans, cats, whales, & bats)

Embryology

Anatomical homologies not visible in adult organisms.

Vestigial structures

Remnants of features that served important functions in the organism’s ancestors.

Homologies at the molecular level

Genes shared among organisms inherited from a common ancestor.