Ecosystems Diversity Natural Selection and Evolution

Adapting To the Environment Species appear to be well suited to their environment Species appear to be well suited to their environment BECAUSE BECAUSE – species that are well adapted to a specific environment will survive No species can willingly adapt itself to its environment. No species can willingly adapt itself to its environment. Adaptation is the result of competition, mutation and natural selection. Adaptation is the result of competition, mutation and natural selection.

What is Evolution? The change in gene frequencies in a population over time 1.Evolution has happened and is continuing to happen. 2.Every species has changed over time. 3.Evolution helps to shape a species and refine the niche for each species in an ecosystem.

Evolution By Natural Selection Three major scientists who developed key scientific understandings for genetics are: Three major scientists who developed key scientific understandings for genetics are: – Charles Darwin – Gregor Mendel – Stephen J. Gould

Evolution By Natural Selection Charles Darwin was a British biologist who lived from 1809 to In 1831 Darwin set sail around the world on a ship called the H.M.S. Beagle to study plants and animals.

Evolution By Natural Selection In 1832, the Beagle stopped in a group of very remote islands called the Galapagos Islands (off of South America). Darwin studied many of the birds there, particularly a small bird called the Finch.

Evolution By Natural Selection Darwin noticed that there were 13 different types of finches on all of the Galapagos Islands, but only 1 or 2 types on each individual island. Darwin noticed that there were 13 different types of finches on all of the Galapagos Islands, but only 1 or 2 types on each individual island. And, Darwin noticed that the different types of finches had profoundly different beaks. And, Darwin noticed that the different types of finches had profoundly different beaks.

Evolution By Natural Selection He realized that the type of beak that occurred on each island related to the type of food that was available on the island. He realized that the type of beak that occurred on each island related to the type of food that was available on the island. So he speculated… So he speculated… At one point a group of finches were “blown on a storm” to the Galapagos Islands. Some of the islands had trees with nuts, others did not. At one point a group of finches were “blown on a storm” to the Galapagos Islands. Some of the islands had trees with nuts, others did not. In that group of original finches, there was genetic variability in beak size and shape. In that group of original finches, there was genetic variability in beak size and shape.

Evolution By Natural Selection Those that had shorter beaks were able to survive on the islands with trees with seeds, whereas those with longer beaks were able to survive on islands with insects. Those that had shorter beaks were able to survive on the islands with trees with seeds, whereas those with longer beaks were able to survive on islands with insects. Over time, the finches that had the evolutionary advantages survived, whereas those with the disadvantage died out. Over time, the finches that had the evolutionary advantages survived, whereas those with the disadvantage died out.

Evolution By Natural Selection Darwin published his Theory of Natural Selection in a book called On Origins of the Species.

Evolution By Natural Selection The Theory of Natural Selection Within every species there is variation amongst the members (some are taller/shorter/etc.). Within every species there is variation amongst the members (some are taller/shorter/etc.). Genetic variability (alleles) Genetic variability (alleles) Most traits reveal considerable variety in their form. Most traits reveal considerable variety in their form.

The Theory of Natural Selection – In every ecosystem, some traits will be favored and some will not be favored because of the biotic and abiotic factors within the ecosystem – Some individuals will be better suited for their environment.

The Theory of Natural Selection – Individuals with traits best adapted for survival in the environment are able to out-compete other individuals for resources. – As a result, over time, those members with the traits that are favored are more likely to survive and have offspring.

The Theory of Natural Selection – Over time, traits best adapted for survival in the environment and the alleles that generate them accumulate in the population. – In turn, the best adapted of these offspring leave the most offspring. – Eventually, if a trait becomes common to all members of a species, the species has evolved

Three Important Components ! 1.Individuals cannot evolve. Populations evolve. 2. Natural selection is the mechanism of evolution. 3.Evolution is situational (NOT GOAL ORIENTED).

Evolution By Natural Selection

Genetics Gregor Mendel ( ) was a Czeck monk/botanist who raised garden peas Gregor Mendel ( ) was a Czeck monk/botanist who raised garden peas He observed that some pea pods had different colors and shapes. He observed that some pea pods had different colors and shapes. As Mendel bred the pea pods, he discovered that certain traits were passed onto the offspring and others were not. As Mendel bred the pea pods, he discovered that certain traits were passed onto the offspring and others were not. Offspring are not a blend of their parents Offspring are not a blend of their parents Father of Genetics Father of Genetics

Genetics DNA is the molecular blue print of the organism DNA is the molecular blue print of the organism An organism gets half of its DNA from its mother and half of its DNA from its father. An organism gets half of its DNA from its mother and half of its DNA from its father. While DNA is a very long molecule, portions of it move together as genes While DNA is a very long molecule, portions of it move together as genes A gene is a segment of DNA that codes for a particular trait. A gene is a segment of DNA that codes for a particular trait. – Dominant genes – when present are responsible for the visual trait – Recessive genes – are overshadowed (not seen visually) but can be passed on to offspring

Punctuated Equilibrium

PATTERNS OF EVOLUTION Parallel Evolution – Two related species making similar evolutionary changes after their divergence. – Marsupial and Placental mammals

PATTERNS OF EVOLUTION Coevolution occurs when 2 or more species evolve in response to each other.

Coevolution Any relationship involving competition creates the potential for coevolution. – Plants and herbivores coevolve in response to each other. – Predators and prey coevolve in response to each other. – Species in competition for limited resources often coevolve.

Evolution by Artificial Selection Many populations of plants and animals do not live in the wild – – Cared for by humans – – People control how they reproduce – – Therefore how they evolve Selective breeding of organisms by humans for specific characteristics is called artificial selection

Evolution by Resistance Sometimes humans cause populations of organisms to evolve unwanted adaptations Sometimes humans cause populations of organisms to evolve unwanted adaptations – Insects resistant to pesticides – Bacteria resistant to antibiotics Resistance is the ability of one or more organisms to tolerate something designed to kill it. Resistance is the ability of one or more organisms to tolerate something designed to kill it. Think about natural selection! Think about natural selection!

Natural Selection in Action  Camouflage

Natural Selection in Action  Eye spots

Natural Selection in Action  Counter Shading

Natural Selection in Action  Mimicry  Monarch or Viceroy Butterfly

What Drives Species to Change?

How do new species arise ? By geographic isolation: By geographic isolation: – This is the way the flora and fauna of the Galapagos Islands evolved. – The barrier prevents gene flow. – When two different species arise this way, it is called allopatric speciation. Greek: allos = other patria = homeland Greek: allos = other patria = homeland

Allopatric speciation of squirrels in the Grand Canyon The valley of the Grand Canyon is a significant barrier for ground squirrels that have speciated on opposite sides, but birds that can move freely have no barrier.

Another Allopatric Example Ring species provide examples of what seem to be various stages in the gradual divergence of new species from common ancestors. Ring species provide examples of what seem to be various stages in the gradual divergence of new species from common ancestors. – In ring species, populations are distributed around some geographic barrier, with divergence increasing as they move.

How do new species arise? By adaptive radiation By adaptive radiation – evolution of many diversely adapted species from a common ancestor. Darwin’s Finches

Sympatric Speciation sympatric speciation sympatric speciation – requires the emergence of some reproductive barrier that isolates a subset of the population without geographic separation from the parent population.

Sympatric Speciation Polyploidy is having more than the diploid number of chromosomes Polyploidy is having more than the diploid number of chromosomes This condition is common in plants and quite uncommon in animals This condition is common in plants and quite uncommon in animals – Non-disjunction in meiosis – It can make offspring reproductively isolated from their parental species. – Cannot breed with diploid members and produce fertile offspring Polyploid population can self-pollinate, mate with other polyploids, or reproduce by asexual propagation. Polyploid population can self-pollinate, mate with other polyploids, or reproduce by asexual propagation. Many plants important for agriculture are the products of polyploidy. Many plants important for agriculture are the products of polyploidy.