ADAPTATION Terms related to Adaptation A trait that

ADAPTATION

Terms related to Adaptation • A trait that improves a population’s reproductive success is an adaptation. • An individual/population that is adapted is successful at producing grandchildren in its environment. • Adaptation is the process by which a population becomes more adapted to its environment. • The process of adaptation includes changes in the genes of the population. • All the genes (and their proportions) in a population is the gene pool.

Adaptations • Adaptations are traits that help the individual, population, and species survive and reproduce in their environment. • Traits may be physical, metabolic, and developmental. • Examples?

Traits • Traits are passed from one generation to the next • That means that all the information to produce all of your traits was contained within the single cell that was you when you were conceived. • What determines your traits?

Proteins • Proteins determine our traits • Each protein is a sequence of amino acids. The length of the amino acid chain and the sequence of amino acids in the chain determine the structure and function of the protein and thus the trait. • Hemoglobin is an example of a protein. Hemoglobin: a protein that is 146 amino acids long Val His Leu Thr Pro Glu Lys … 139 more

DNA • DNA is the recipe book for making proteins (and therefore traits). This is what is passed on from one generation to the next. • How does DNA code for proteins, thus traits? DNA Proteins Traits

DNA is arranged as a double helix • It is composed of four types of nucleotides: A Adenine T Thymine G Guanine C Cytosine

The sequence of nucleotides along the DNA molecule provides the recipe specifying the sequence of amino acids to put together to make each type protein. This is like the sequence of letters in a recipe specifying the ingredients to put together to make the final dish.

More on DNA • • • A-T T-A C-G G-C T-A every three nucleotides (codon) codes for one of the 20 amino acids (and there are 1000 s of nucleotides in a strand of DNA)

Translation (from DNA to m. RNA to Protein • A copy of the DNA is made (called m. RNA) so that the original isn’t messed with. The m. RNA is like the DNA except the T nucleotide is replaced with a U nucleotide. • Readers go along the m. RNA and when they find a particular sequence of nucleotides (the start codon), they begin to read each codon and put together the specified amino acids until they hit a stop codon which causes the protein to break off. Video 2 on DNA translation

THE GENETIC CODE Thymine (T) is replaced with Uracil (U) in messenger RNA.

Genes are translated into proteins based on a triplet code Transcription Codon = 3 bases Translation Protein = many amino acids strung together Amino acid

• DNA is composed of nucleotides Recap – There are only 4 types of nucleotides • Every 3 nucleotides codes for an amino acid – There are 20 different amino acids • Strands of amino acids form proteins • Proteins are responsible for traits and adaptations… Video 2 on DNA translation

Chromosomes • So what is a chromosome?

Chromosomes • Strands of DNA, all tightly wrapped up and existing in a cell’s nucleus • [Humans have 46 chromosomes, 23 from each parent]

Genes • So what is a gene?

Genes are a particular segment of DNA, that code for a protein (usually). Junk DNA

Genes • Genes are – A section of DNA that encodes information for building a protein (or RNA molecule) – Each chromosome can have thousands of genes on it.

Mutations • What is a mutation?

Mutations • Mutations are a change in the sequence of nucleotides in a gene. • Mutations are random, caused by • Chemicals, radiation, copying errors • Mutations change the protein that is specified • Mutations may be beneficial, neutral, harmful, or lethal

Alleles are variants of genes

Sickle cell disease • Occurs due to a mutation in the gene that codes for the hemoglobin protein that carries oxygen in red blood cells. • Causes the normally round red blood cell to change into a sickle shape that no longer carries oxygen as well. This can be lethal. Red blood cells of affected individuals distort in shape, break down or clog blood vessels and cause pain, poor circulation, etc Val His Leu Thr Pro Glu Lys … 139 more Val His Leu Thr Pro Val Lys … 139 more

Sickle cell disease • Alleles: different versions of genes. – – Sickle cell allele (h) “normal” allele (H) Sickle Cell Anemia (hh): often lethal Sickle Cell Trait (Hh): symptoms vary, usually very little effects. Mom H Dad h HH Hh Hh hh

Sickle cell disease • Is having the sickle cell allele good or bad?

Sickle cell disease • Is having the sickle cell allele good or bad? – It depends on the environment!! – The sickle cell allele confers genetic resistance to malaria, one of the biggest killers of infants in areas with malaria. • So, where do you think you find populations with the highest incidence of the sickle cell allele? Areas with Malaria. PBS Video

Gene pool • Gene Pool: all of the alleles and their proportions in a population.

Gene pool • Gene pools change over time. 80% 20% Environmental Change – Pesticide introduced 0% 100% Resistant Gene

Gene pool • A change in a gene pool over time is called what?

Evolution • Genetic Evolution: a change in a gene pool – Note: this operates at the population level! Another definition is a genetic change in a population.

What causes gene pools to change? • Mechanisms of evolution – – Mutation Migration (Gene Flow) Chance (Genetic Drift) Natural Selection

Mechanisms of evolution • 1. Mutations: produce new alleles and new genes. – – are random cannot be predicted ahead of time create genetic variety may be beneficial, neutral, or harmful to the individuals that inherit them

Mechanisms of evolution 2. Migration (immigration/emigration). – Technical term is gene flow. – The movement of alleles between populations as a result of movement of individuals from one population to another.

Mechanisms of evolution 3. Chance: when chance, rather than traits determine reproductive success. Example: disaster that kills part of a population. Small populations are more susceptible to big evolutionary change due to chance. Technical term is Genetic Drift.

Mechanisms of evolution • 4. Natural Selection: When traits determine reproductive success; traits in more reproductively successful individuals get passed on more into the next generation.

Natural Selection • Natural Selection: Alleles that confer “success” are more likely to be passed on to future generations and will increase their % relative to other alleles over time. Technical term for “success” is differential reproductive success.

Example of Natural Selection Resistant Allele • Gene pools change over time. Alleles 80% 20% Environmental Change – Pesticide introduced 0% 100% Non-Resistant Allele

Example of natural selection • Beetles and pesticide resistance – The resistant and non-resistant alleles were due to past mutations that created genetic variety in the beetles but were neutral until now (pesticide spraying time). – The pesticide acted as a new environmental selection pressure that selected for the resistant allele. – This selection pressure, causing individuals with the resistant allele to out-survive and out-reproduce individuals without the resistant allele, resulting in an increase in individuals with the resistant allele in the next generation.

Natural Selection http: //evolution. berkeley. edu/evolibrary/article/0_0_0/evo_14

Natural Selection Peppered Moth Simulation With lichens on tree before pollution Without lichens on tree because pollution killed them http: //faculty. etsu. edu/jonestc/Virtualecology/Models/Moths. html

Natural selection flowchart New Genes Random Recombination New combinations of existing genes Sexual reproduction Genetic Variability—Gene Pool Current mix of genes in population Environmental Selection Pressures Reproduced Genes Mutation Examples: climate, predation, mate selection Differential Survival Differential Reproduction Some genes and gene combinations help the individual survive better than other individuals. Some genes and gene combinations help the individual reproduce better than other individuals

Natural selection flowchart • Mutation and recombination create genetic variety in gene pool of a population. • Mutations: create new alleles/genes. • Recombination: sexual reproduction mixes alleles and creates new combinations of alleles.

Variation arises from Mutation: new genes Sexual Recombination: new gene combinations

Natural selection flowchart • Environmental selection pressure: affects the survival and reproduction of individuals in a population differently (think back to the beetles)

Natural selection flowchart • Environmental selection pressure leads to differential survival and differential reproduction of individuals with more successful alleles. This is passed on to future generations and changes the gene pool through time.

“evolution: survival of the fittest” • Isn’t that we were taught in school? Well, its wrong. • This is an example of science being misinterpreted by the public.

“evolution: survival of the fittest” • What does fittest mean? – To a biologist? – To the public?

“evolution: survival of the fittest” • What does fittest mean? – To a biologist? • = differential reproductive success – To the public? • = biggest, strongest, ….

“evolution: survival of the fittest” • What does fittest mean? – To a biologist? • = differential reproductive success – To the public? • = biggest, strongest, …. • ALL that really matters is whether or not your genes are passed on to future generations ….

Artificial Selection

Types of evolution • 1. Divergent evolution • 2. Convergent evolution • 3. Co-evolution

Divergent Evolution • 1. Divergent evolution – Two different populations of a species that experience different selection pressures may as a result become genetically different from one another • Once in a very great while, the two populations will become so different that they cannot reproduce together anymore (this then becomes speciation).

Divergent Evolution

Divergent Evolution

Divergent Evolution

Divergent Evolution http: //www. biology-online. org/images/darwin_finches. jpg

Divergent Evolution

Convergent Evolution • 2. Convergent evolution – Start with two very different species; they experience similar selection pressures and through time come to look and/or behave similarly.

Convergent Evolution Fish Reptile Mammal What is the similar selection pressure?

Convergent Evolution

Convergent Evolution What is the similar selection pressure? http: //www. votawphotography. com /photo/Animals/animals. htm Speed to catch prey (cheetah) and speed to win races and be bred. http: //www. hundekosmos. de/images/greyhound_517. jpg

Convergent Evolution Placental Mammals Marsupial Mammals

Convergent Evolution “Ant eaters” of the world

Convergent Evolution Many plants look like cacti because they also have evolved to store and defend water but they are not cacti – for example, the ocotillo is not a cactus, it is a shrub in a different plant family.

Types of evolution • 3. Co-evolution – Two species that interact with each other (predator/prey; mutualistic; parasite/host; …) and act as selection pressures on one another – “Evolutionary Arms Race” Long legs Good hearing Sharp eyesight

Coevolution