INTRO TO BIO evolution and natural selection

Gene

a segment of DNA with the instructions for making a specific protein 

Allele

A different version of the same gene 

How are genes and alleles related?

Genes are specific segments of DNA that provide the instructions for a trait, while alleles are the different variations or forms of those genes. 

How are alleles related to the traits that an organism has? 

Alleles are different forms of genes that make the body look and function differently.

What causes traits to vary in a population? 

Evolution

Evolution

a change in allele frequencies in a population over generations 

Natural Selection

Individuals better suited for survival and reproduction in their environment, and those traits becoming more common

What conditions must be true in order for natural selection to occur?  

Variation, heredity, and differential reproduction  

evolutionary fitness

an individual’s lifetime reproductive output, compared to other members of the population 

artificial selection

humans determine which traits result in highest fitness that they want to reproduce 

general circumstances under which we are able to directly observe evolution

We can directly observe evolution when organisms have very short generation times, reproduce rapidly, or experience intense environmental pressures. 

homologous structure

Structures that have different functions, but the same origin. 

analogous structure

structures that have the same functions but completely different evolutionary origins.  

Vestigal structure

a structure that no longer has a function, it is stil present because it was inherited from an ancestor that had it. 

How does the fossil record provide evidence for evolution? 

Gradual changes in structure 

Poinsettia “flowers” and cactus spines are both derived from leaf tissue. This means the same set of genes that makes leaves were evolved in different ways to result in these structures, making them:

homologous

Shark and dolphin body shape is ________ : 

Analogous