Ms. Hughes

 Evolution is the process by which a species changes over time.  In 1859, Charles Darwin pulled together these missing pieces. He was an English naturalist who studied the diversity of life and proposed a broad explanation for it.

 A theory is a broad explanation that has been scientifically tested and supported.  Modern evolutionary theory began when Darwin presented evidence that evolution happens and offered an explanation of how evolution happens.

 Beagle  Galapagous  Finches  Descent with modification

 If a trait can be inherited, breeders can produce more individuals that have the trait. Breeders simply select individuals that have desirable trait. Breeders simply select an individual that have the desirable traits to be the parents of each new generation. This process is called artificial selection because it is done by humans not natural causes.

 Most people believed species were created and stayed the same forever.  Lamarckian Inheritance ◦ Each organism is usually well adapted to it’s environment so organisms adapt over time to adapt to their environment.

◦ Malthus pointed out that food supplies were being produced linearly and populations were increasing exponentially. ◦ So organisms were being produced faster than the environment could supply nutrients and resources for them. ◦ The amount of organisms in a population is limited by the amount of resources available to that organism.

 Every living thing has the potential to produce offspring but not all of those offspring are likely to survive and produce offspring.  Individuals that have traits that better suite their environment are more likely to survive.  Darwin proposed that natural selection is a cause of evolution. In this context evolution is a change (gradual) in the inherited characteristics of a population from one generation to the next.

 Overproduction  Variation  Selection  Adaptation  Write a few words that explain each (page 380)

 Each habitat has its own challenges  Those who survive those “challenges” are available to pass on their traits – they have been “selected” for  Each species becomes adapted to its environment as a result of living in it over time.  Adaptation – inherited trait that helps the individuals survive and reproduce.  Evolution is a gradual process of adaptation!  This applies to populations and species NOT INDIVIDUALS!!!!

 Darwin presented a unifying explanation for data from multiple fields of science.  Fossil Record  Biogeography  Developmental geography

 You can infer events by looking at fossils which make up the “fossil records”  Comparing fossils and living being reveals a pattern of gradual change from the past to the present  Intermediate form between species can be found. These are know as intermediate species.

 The study of the locations of organisms around the world.  Darwin saw similarities of species all around the world.

 The ancestry of organisms is also evident in the ways that multicellular organisms develop from embryos – embryology.  These similarities are most likely due to a common ancestor.

 The anatomy of most vertebrates is very similar.  Define and give an example of a homologous structure.

 Genes can change by mutation and that such change can make a new varieties appear.  Then natural selection may select against or for others in the habitat and specific traits.

 Darwin’s work had three major strenghts:  Strengths – 1  Weakness - 2

 Discoveries since Darwin’s time, especially in genetics have been added to his theory to explain the evolution of species.

 Can an individual evolve?  IS evolution survival of the fittest?  Is evolution predictable?  Answer these questions and give a reason as to why or why not.

 Because it affects every aspect of biology, scientist can study evolution at many scales. Generally these scales range from microevolution to macroevolution with speciation in between.

 Define speciation  Turn to page 388 and look over patterns of micro and macroevolution

 Population genetics – the study of microevolution.  Microevolution can be studied by observing changes in the numbers and types of alleles in populations.  Macroevolution – speciation - microevolution

 Biologists study polygenic phenotypes by measuring each individual in the population and then analyzing the distribution of the measurements.  Define distribution on page 400  Discuss bell curve

 To study population genetics, we need to study how genes in populations change over time.  The particular combination of alleles in a population at any one point in time makes up a gene pool.

 Genetic variation and change are measured in terms of the frequency of alleles in the gene pool of a population.  Define frequency on page 401.

 The major source of new alleles in natural populations is mutation in germ cells.  Why germs cells and not somatic?

 Who is Hardy Wienburg – read paragraph on page 404.

 Genetic change in a population can be measured as a change in genotype frequency or allele frequency.  Hardy Weinburg principle predicts that the frequencies of alleles and genotypes in a population will not change unless at least one of five forces acts upon the population.

 1 – gene flow  2- nonrandom mating  3- genetic drift  4 – mutation  5 – natural selection

 Sexual reproduction creates the possibility that mating patterns or behaviors can influence the gene pool of a population.

 Allele frequencies are more likely to remain stable in large populations  Define genetic drift and give an example

 How selection acts ◦ All populations have genetic variation ◦ Individuals tend to produce more offspring than the environment can support ◦ All populations depend upon the reproductions of individuals.

 Natural selection acts only to change the relative frequency of alleles that exist in a population.  Indirect force ◦ Natural selection acts on genotypes by removing unsuccessful phenotypes from a population.

 Three major patterns are possible in the way that natural selection affects the distribution of polygenic characters over time. These patterns are  Directional – 1  Stabilizing – 2  Disruptive - 3

 Today scientists may use more than one definition for species. The definition used depends on the organisms and field of science being studied.  Biological species concept – must be able to interbreed and produce viable offspring.  This does not apply to asexual organisms.

 Speciation has occurred when the net effects of evolutionary forces result in a population that has unique features and is reproductively isolated.  Brief discussion on mechanisms of isolation page 413

 The species that exist at any time are the net result of both speciation and extinction.  Mass extinction vs. punctuated extinction.

 Page 428  Grouping organisms by similarity is often assumed to reflect phylogeny, but inferring phylogeny is complex in practice.  Define phylogeny