bio 12,13,14
What does "Survival of the Fittest" Really Mean???
"Survival" may not mean survival The male praying mantis dies in the act of copulation When the female bites the male's head off and eats him The male Australian Redback Spider Summersaults his abdomen into the jaws of his mate during copulation And she kills and eats him This is NOT survival . . . but still fits the definition Why is this still "Survival of the fittest" And why would the system lead to the males being eaten ? Bee Drones . . . . These acts may increase the amount of time spent in copulation Possibly increasing the number of eggs fertilized Furthermore, -- the additional nutrition the female gets If they eat their mate may increase The chance of offspring survival - because the nutrients for the eggs is greater And remember. . . "The fitness of an individual is measured By how reproductively successful its offspring are ------ In the next generation"
what would account for the "Fast and Slow" of Punctuated Equilibrium?
#1. A rapid time of speciation may occur when some members of a population Inherit a key adaptation that gives them an advantage An example. . . the oldest flowering plant fossil is from about 125 million years ago The advantage of flowers would have been an increasable leap toward successful sexual reproduction. . . . From that time forward plants that flowered - diversified quickly That is shown in the fossil records of 100 million years ago Where there are MANY fossils or flowering plants #2. Rapid speciation may also occur when something catastrophic occurs. . . Killing many species and opening many niches to the surviving species There is, -- for a while - very little competition for the use of these niches Organisms move in and reproduce quickly Eventually the size of the populations.. creates competition For the resources- - - and additional natural selection occurs. The fossil records actually support both Punctuated Equilibrium & Gradualism Horses, Foraminiferns, diatoms and other species Have a virtually unbroken fossil record that shows their gradual evolution
Postzygotic Reproductive isolation
- after the fertilized egg is produced Sometimes pre-mating isolating mechanisms fail Or have not yet evolved So fertilization & Reproduction can and sometimes will take place Between two different species If pre-mating mechanisms are not in effect Then . . . maybe post mating ones are 1. Hybrid Inviability = Zygote Mortality Developing hybrid... the embryo ... dies Before reaching maturity; hatching; being born. This usually occurs because the genes of the parents are incompatible 2. Hybrid Infertility = Hybrid Sterility The hybrid survives... but is not able to reproduce. What often occurs in these animals - - - Is that meiosis cannot occur in the hybrid Because the number of chromosomes that one parent contributes Is different than the number the other parent contributes Preventing the production of gametes Mules = horse x donkeys; ligers = male lion female tiger Tigon = male tiger x female lion; --- Zorces --- Beefalow 3. Hybrid Breakdown or Poor F2 fitness The hybrid is fertile .... But the next generation The F2 generation is poorly suited to its environment "Neither fish nor foul" Coy-wolf // Northern gray wolf only --- vs. other wolves who kill coyotes Post mating mechanisms are especially important in lower animals And in plants... Where fertilization is external from the body Example; many fish and other aquatic organisms Release sperm and egg into the water Plants have pollen carried by insects or by the wind From plant to plant If Gamete Incompatibility doesn't work. . . Maybe one of these mechanisms does When two separate groups can no longer reproduce They begin to follow their own independent patterns of evolution
Most fossils and fossil records are incomplete - because
1. Most organisms never form fossils Especially organisms with no hard structures Because they are likely to have been eaten Or totally decomposed by bacteria or fungi after death 2. Erosion and the movement of the earth's continental plates Glaciers etc. have destroyed any fossil or parts of the fossils that may have once existed 3. It is difficult to discover fossils that are buried deep in the earth Or submerged under water.
There are 4 ways new information can be introduced into a species or population
1. Mutation = the ultimate source of all change (like the lighter and lighter color of humans - right vs left handed) 2. Recombination and nonrandom mating Sexual selection by competition or Female choosing a mate 3. Migration = Gene Flow 4. Gene Drift - there are 2 types Founder effect and Bottle Neck All occur frequently and All would disrupt Hardy-Weinberg's Equilibrium
Weinberg and reality
1.Individuals remain in closed groups (towns, locations, coral reefs) mating among themselves rather than in the larger population So mating is not often "really" random. Courtship in more advanced animals means some males never mate non random mating 2.Mutation is a constant and random occurrence New alleles are always being introduced 3.Individuals migrate out of one population and into another. You go off to college --- or get a job 4.Some phenotypes are better than others ... and there will always be limited resources ... so, competition and Natural selection is a given. 5.Gene drift occurs, causing random change in the allelic frequencies. This not adaptive . . . but natural selection can only choose from the alleles that exist ... not from what used to exist
Weinberg's Requirements
1.The gene pool must be large And mating must be random. This does happen with both plants and animals. Swarming, external Fert, Plants w/ windblown pollen.... Many aquatic animals with open release of sperm and eggs. 2. No mutation can occur 3. There can be no gene flow = no migration into or out of the population 4. There can be no natural selection 5. Gene drift cannot occur. Gene drift can be two different things Chance sampling --- and Bottle Neck
Absolute Dating - using Carbon 14
1st used to date the tombs of two Egyptian Pharaohs The Carbon-14 dating determined they had both lived around 2800 B.C. + 250 years ... Or 3050 B.C. to 2550 B.C. So within the time range of the known existence of the two Pharos. And very accurate for people who lived 5000 years ago. All radioactive isotopes have a ½ life That amount of time required to change ½ of the radioactive substance Into another stable substance 14C is the ONLY radioactive substance found in organic matter The ½ life of 14C is 5,730 years and 14C 14N So, if we know what the ratio of 14C vs. 12C was in an organism when it died And it is assumed that this ratio at death does Not change over time --- which is untrue but close enough. . . Then we should be able to tell how that ratio has changed over time If the ratio of 12C to 14C is 100 to 1. At time "zero" there are 10,000 12C for every 100 14C. After 5730 years. . . there is NOW 10,000 12C for every 10 14C After another 5730 years there is 10,000 12C for every 1 14C You get a ratio of 12C to 14C in the fossil And you can compare it to the ratio of 12C to 14C in organic matter today And you can calculate backwards 10: 10,000 = recent death 10: 40,000 = two ½ lives = 11,460 years 10: 20,000 = one ½ life = 5,730 years 10: 80,000 = three ½ lives = 17,190 years etc 14C dating is not useful For dating organisms older than 50,000 years Which is over 9 half-lives of 14C Because the remaining 14C is so small --- it is meaningless So, the ratio of 40K (potassium) with a ½ life of 1.3 billion years To 40Ar (argon) is used on the rocks surrounding the fossils When things are recent, years are important With something like babies, months or days are important When things are really old . . . plus or minus 100 years may not be significant Before 14C dating was possible, Scientists began
There have been 5 major mass extinctions - since life evolved on earth
450 MYA - Ocean levels radically changed, Lasted 10 million years & 85% of all species disappeared 380 MYA - global cooling O2 loss Lasted 3 million years, 83% of all species disappeared 250 MYA - Impact & volcanic activity Lasted an unknown period of time and 95% of all species disappeared 210 MYA -- Global warming, volcanic activity Lasted 3-4 million years, 80 percent of all species disappeared 65 MYA --- Impact and volcano this is the extinction of the Dinosaurs - 76% of species Lasted less than a million years
Vestigial Structures
A vestigial structure is a structure that has no function in the species where it is found In humans, the appendix, wisdom teeth, coccyx are all considered vestigial Depending on ethnicity 11 to 45 percent of the population are missing some or all of the wisdom teeth And ear muscles are all vestigial Human embryos have tails that disappear in the womb Whales and snakes have vestigial and tiny leg bones Where their legs once were Vestigial structures are also homologous to fully functioning structures inherited by related lineages. Thus, they provide strong evidence of common ancestry And can help us trace the evolutionary origin of the species with the vestigial structures.
Cheetahs have undergone several population bottlenecks
About 10,000 years ago the cats were common in many areas of Africa Today there are two isolated population Of only about 7,100 animals left in the wild. (2022 count) Inbreeding has made the South African Cheetahs so genetically alike That even unrelated animals Can accept skin grafts from each other There have been two known bottle necks Which account for this genetic uniformity One occurred at the end of the most recent ice age Which ended about 12,000 years ago (Little Ice Age 1550-1850) This ice age drastically changed the cheetah's habitats The second bottle neck occurred when humans slaughtered Thousands of cheetahs during the 1800s For the fur trade - making coats etc.
Wallace's Line
Alfred Russell Wallace noticed a distinct difference in birds and mammals On either side of what became known as "The Wallace Line" Found in the Malay Archipelago This difference turns out to be caused by a deepwater trench That separated the islands of this region Preventing migration of most species across this "Line" This helped produce a unique variety of organisms on both sides of the Wallace line
Polyploidy is where the number of chromosomes increases
And is an isolating mechanism seen only in plants Making their gametes incompatible with plants that have not undergone the "N" number increase Over 50% of all flowering plants and 95% of ferns show Polyploidy Important crops like; wheat, corn, sugarcane, potatoes & coffee Are polyploidy This form or reproductive isolation Seems to be very important in plant evolution In animals.... Polyploidy seems to be rare And usually causes sterility or embryonic termination
Natural Selection and Adaptation
Are a response to living and nonliving factors Is the nonliving environment -- too hot, too cold, too dry, too wet, too anything In the environment of all populations An animal or plant has to deal with What it eats What eats it So, predator--- prey responses Both change over time There is usually a Co-Evolution Q The plant gets thorns or poisons -- to protect against the predators These predators which are herbivore evolve tougher lips and tongue Or a tolerance to the poison Or ---- they find a different food
Humans conduct Artificial Selection (animal and plant breeding)
Artificial Selection Has a Goal
Microevolution
Changes that occur over a much shorter period of time a relatively new concept Even just several years - - - or several generations Making this type of evolution observable.
Charles Darwin
Charles Darwin is given credit today for developing and publishing The concepts of Evolution by Natural Selection Darwin was hired in 1831 as the Naturalist on the HMS Beagle - about 190 years ago The ship made a 5 year voyage to explore and map the world What Darwin saw on the trip helped him develop his theory Which he worked on until 1858 - over 20 years When he received a manuscript from Alfred Russell Wallace Also a British Naturalist Wallace, through independent research and travel Also developed the theory that Natural Selection is the driving force of evolution In 1859, Darwin published: "On the Origin of Species by Means of Natural Selection Or, Preservation of Favored Races in the Struggle for Life" And Wallace was listed as second author Darwin also often credited him, when discussing Natural Selection No two authors thrown together in such a fashion Tried harder than Darwin and Wallace to treat each other fairly. Wallace greatly admired On the Origin of Species. In turn, Darwin regarded Wallace as the one man who truly understood the idea of evolution By natural selection. They did not, however, always agree Now..... keep in mind this is the mid to late 1800s --- It was not until the 1930s that scientists finally recognized The connection between genetics and natural selection And not until 1953 that we discovered the actual structure of DNA So, Darwin and Wallace were making some fantastic intellectual leaps about Evolution Way before there was some important information available to support These intellectual leaps
The Origin Of Elaborate Coloration Is Unknown. One Possibility Is;
Coloration may have started as an indicator of health It takes energy to produce and maintain this type of coloration And longer feathers or antlers and horns which are often shed after the breeding season . . . An organism that was unhealthy or weak Probably could not do it The same could be said for the victor of direct competition For the right to reproduce
Compare various biological molecules
DNA, proteins, RNA etc. Beginning in the 1960s and 70s scientists began the sequence analysis of DNA They also began looking at proteins and other biological molecules Since then, . . . the explosion of molecular data Has revealed in unprecedented detail How species are related to one another It has also corrected many things we had wrong Whenever the same conclusion can be drawn from independent data. . . . It helps substantiate the conclusions..... and the Scientific Theory of Evolution It is because of Common Descent . . . . That all living things share fundamental characteristics --- Cell membrane --- other membranes - DNA, RNA, Ribosomes, Proteins --- The 5 characteristics of life - etc. - Remember we talked about how the definition of a "Cell" has changed??
SPECIATION MAY BE GRADUAL- - - or- - - OCCUR IN BURSTS;
Darwin's vision was Evolution is a a gradual change Which transforms one species - or one population into another species This theory has become known as Gradualism Gradualism = evolution proceeds in small, incremental changes over many generations However, in 1972 two Paleontologists Stephen Jay Gould and Niles Eldredge, used the terms Punctuated Equilibrium To describe a different theory of evolution Punctuated Equilibrium = in which they hypothesized That sometimes species don't change for a long time .... Then --- there are relatively brief bursts of rapid evolutionary change Interrupted by, AGAIN, long periods of very little change Both theories are probably right If gradualism is correct. . . the fossil record should show Slow and relatively steady changes Many of the fossil records suggests something different . . . There are many gaps in the fossil record - This might be due to poor preservation of those fossils Because of natural forces destroying them Or maybe - - they just haven't been found yet - - - Punctuated equilibrium provides a different explanation To the absence of fossils showing the gradual change Gradualism would produce Maybe.... There were just too few of these transitional organism To produce a fossil record Periods of rapid biological changes Would not leave significant fossil evidence of any single intermediate form And again - -- - Both Theories Are Probably Right
Natural Selection - vs Artificial Selections by humans
Dogs vs. wolves artificial selection is done with foresight & purpose. Dogs, cats, flowers, cattle for beef vs. milk, chickens, vegetables, grains etc. Breeders choose traits they like -- and want That already exist within the species And continue to select for these traits in the offspring of their crosses Humans have a goal with artificial selection Unlike artificial selection ----- Nature has no goal
Limited resources
Every habitat contains limited resources required for survival and reproduction - like food, water, reproductive locations, sunlight etc
Population
Evolution occurs within a Population of a Species not within individuals. . . Because Once the egg is fertilized - the genes are set So individuals do not evolve because their information can't change
Extinction
Extinction occurs when all members of a species are dead There can be many causes. . . . But the end result is Usually --- that the extinct species have failed to adapt To environmental pressures In a natural situation any species - - - all species Will vanish if the gene pool does not contain the "Right" alleles The "Ones" necessary to sustain the population And produce fertile and sufficient offspring Biologists have identified and described about 3 million species But - - there are probably 14 to 100 million species in the world There Are Two Types Of Extinction Events #1 Background extinction - Extinctions that occur without human impact Is the rate of extinction that results from gradual loss of species as their population shrinks Because they are confronted with new challenges Paleontologists have used fossil records To calculate that this type of extinction Is estimated to occur at a rate of 0.1-1.0 extinctions per year, per million species #2 Mass Extinctions = a large number of species disappear Over a relatively short period of time Mass extinctions are important because, when they happen A huge number of new habitats open For the surviving species available to fill them TYPES OF MASS EXTINCTIONS #1 - Impact theory - - - meteorites or comets have twice hit the earth Sending dirt, soot and debris into the sky These particles blocked the sun And began a chain of events that leads to the death of many organisms And the extinction of many species There is evidence - including layers of rock that include Iridium An element rare on earth . . . but common on meteorites #2 - Plate tectonics, - - - which we talked about Would account for other periods of mass extinctions By the introduction of more advanced species of plants and animals To continents where they had not existed before
Genetic Drift Occurs by Chance & Reduces Genetic Variation
Genetic drift is a change in the frequencies of alleles Brought on Only by chance It decreases the number of alleles in a population Gene drift is based on sampling errors And is more likely to affect small populations than large ones There are 3000 organisms in a population and 50% die you still have 1500 individuals (probably a large gene pool) There are 300 organisms in a population (already a small number) 50% die - there are now only 150 individuals - a very small gene pool.
Homologous Structures Have Shared Evolutionary Origin
Homologous structures are structures that had the same origin - - - But are now used for different functions The front limbs of a bat, bird, lion, dolphins, and humans Are all homologous structures --- When you can show structures exist In very dissimilar species And are often used in very different ways . . . You can show relationships between these species
Postzygotic Reproductive isolation
Hybrid Viability Hybrid Sterility Hybrid Breakdown
Speciation can occur
If a population or members of a population Become Allopatrically = geographically-----Isolated From other populations of the same species Allopatric Speciation --- Geographic Barriers between the 2 populations With allopatric speciation... A physical barrier separates a population Into two groups that cannot interbreed -- Because of the barrier The isolation can be caused by rivers, deserts, great distances Glaciers, changes in sea level etc. Remember - - - Production of genetic info = mutation, migration, recombination Reduction of genetic information = natural selection and genetic drift
Adaptations Enhance Reproductive Success
If every member of a population is different (asexual reproduction the exception) From all other members of that population. . . . . If more offspring are produced than the environment can support. . . . The struggle for survival between individuals of this population IS A GIVEN They are competing. . . . and there is not enough -- NEEDED "stuff" The variations within the population - - - - Means that some individuals are better suited to the current environment than others Better able to get nutrients, water, avoid predators, attract mates Hold territory, protect offspring resist diseases etc If some or all of these abilities are controlled by genetics If these genes are passed on to offspring --- in various combinations Each generation is better and better adapted to their habitat Giving some -- in that population -- a "selective advantage" over others in the population Think about you; better at sports, math, art, music, at speaking, at driving, at shooting a gun etc. Species can become better adapted to an existing environment Or they can adapt to an environment undergoing change.
Chance Sampling Sampling Errors
Imagine, in a small population A certain allele of a gene does not occur frequently Now imagine that individuals with this allele Either do not reproduce or do not pass this allele Along to the next generation That allele would no longer be found within the population
Convergent Evolution:- - - Superficial Similarities
In addition to Divergent Evolution You should be aware of Convergent Evolution This is where 2 species look alike Because they have adapted to similar environments -- In similar ways These two species are not closely related --- and may even be unrelated. Good examples include - - - dolphins, penguins and sharks All are marine, and predatory Their adaptations include; streamlining The shape and locations of fins or flippers And coloration The Sahara has a snake related to the cobra that looks like the American Sidewinder The American sidewinder is a pit viper and the one from Africa is a cobra (Elapsid)
Sexual Selection Directly Influences Reproductive Success
In many species the sexes look alike dogs cats etc In other species there can be sexual dimorphism Differences between the appearances of sexes One sex may be much larger, or more colorful than the other, Or have distinctive structures like horn, antlers, or a main
Natural Selection Eliminates Phenotypes
In the Amazon there is a species of orchids % That has an odor that is similar to that of a species of female wasp % The male wasp will selectively visit that species of orchid's flowers --- searching for a mate % And he will visit those flowers -- of that species that more strongly and more specifically smell like the female % Because of this odor. . . . and will pick up pollen % And carry it to other orchids of the same species % Pollinating those orchids - increasing the offspring of the orchids with the strongest most accurate smell Advantages - and Potential Problems for the Orchids % Pollen is moved just within that species of flower --- good - no out crossing % Many orchids are pollinated - good - LOTS OF OFFSPRING # If the wasp goes extinct --- the orchids could also soon follow - because of no pollinators -- bad # Also, the range of the orchid is limited to range of the wasp species -- possibly bad # For the wasp . . . it could be a little frustrating # Lots of effort ... some risk .. no reproduction
There will be a struggle for existence
Individuals compete for the limited resources that are necessary for survival and reproduction- - - some will succeed - - - some will fail
The Concept of Mutation
Is often misunderstood Nature does NOT introduce a mutation into a population "Just in time" to deal with a new condition Resistance to a pesticide by an insect species Or resistance to an antibiotic by a disease causing bacteria Doesn't happen just because these organisms NEED that new gene Nor does the pesticide or antibiotic "Create" the new gene The use of the chemical - selects for those insects or bacteria That have this "unused.... And unusual" information in their genetics These organisms survive to reproduce... Passing this "now advantageous" information On to the next generation in greater and greater quantity Than would have happened before --- it became advantageous Helping to establish a "Founder Population" --- which we will talk about with Gene drift... Mutation affects evolution Only if it is passed on to subsequent generations --- Meaning that the gene must end up in either the sperm or the egg That then becomes an individual That also survives.... And reproduces Passing on that mutation Somatic mutations --- like lung or skin cancer etc Are usually triggered by exposure to something And body cells do not end up in the gametes These kinds of mutations are not a factor in evolution.
Evidence of Evolution
Is seen in the Fossil Records - - - Fossils are the remains and traces Or any other evidence of past life Most records consist of hard parts; Like Bones, Shells, Teeth - Because these structures are not usually consumed Or digested by scavengers And they don't decompose after death Most fossils are found embedded in sediment Sediment is what happens when rock erodes Is usually carried by water and wind to low and protected areas And ultimately produces an accumulation of particles that vary in size People have known about Fossils since the 1400s or earlier They were found when digging was done For agriculture, road building etc. . . . However, most thought these fossils were just ordinary rocks That had been modified by wind, rain or people So that they looked like life forms or a part of a life form Eg. - some clouds in the sky "look like" something .
Polymorphism
Is the co-existence of two or more forms in a population Balanced Polymorphism occurs when the frequency of the varied forms Remains unchanged generation after generation The environment can vary and call for different adaptations At different times --- from the species that live there Members of a species can be Generally Adapted Never specializing for any particular season Or, they can be polymorphic Having a different phenotype for each season Like the arctic hare, which is white in the winter and brown in the summer
dimorphic features
May seem to violate natural selection The bright colors of a male peacock or male cardinals Make the males obvious and more vulnerable to predators And with the peacock also compromises their ability to fly
EMBRYONIC DEVELOPMENT PATTERNS & EVOLUTION CLUES
Molecules Reveal Relatedness: DNA & Proteins Since the 1970s Researchers began to compare the molecules between organisms To help identify relatedness DNA can now be sequenced And that ability has allowed us to compare this information Between species for differences and for similarities Proteins sequences also help support fossil and evolutionary relationships One study showed 7out of 20 proteins To be identical in humans and chimps 33% Many other have only minor sequence differences It is best to compare proteins we all have in common Cytochrom c - - - which is part of the electron transport chain in aerobic cellular respiration in Mitochondria Shows the greatest similarities in closely related species Molecular Clocks DNA can act as a "Clock" If biologists know the rate of mutation for specific genes And the differences in the DNA sequences For that gene in any two species. . . For example, human and chimp genes differ In about 4% to 6% of their nucleotides And substitutions occur at an estimated rate of 1% per 1 million years Therefore, -- about 4 to 6 million years have passed Since the two species diverged from a common ancestor Molecular clock studies are complex, DNA replication errors occur at different rates In different regions of a chromosome So, it was discovered that using the genes that encode for Ribosomal RNA Is the best information to use for these comparisons Ribosomal RNA is common to all organisms . . . And slow to mutate making it a good
Over production of offspring
More individuals are born than can survive and reproduce.
Mutations Fuels Evolution
Mutations are the only ORIGINAL source of gene change --- And the only change that occurs in organisms that reproduce only Asexually They are a Random change in an organism's DNA Introducing a new allele to a population ↑ This new allele may be harmful, neutral, or beneficial And they can be Dominant or Recessive Depending on its affect on the encoded protein And the environment at the time.... BUT - because the change is Random.... And organisms have evolved for a long time To existing conditions The change is frequently harmful
Natural Selection Can Shape a Population
Natural Selection Can Shape a Population In Three Ways 1. Stabilizing Selection = is where the extreme phenotypes are less fit Q Than the intermediate phenotype. Human birth weight The natural selection pressures are consistent for a long time 2. Directional Selection = one of the more extreme phenotypes is the fittest The rise of antibiotic resistance among bacteria or Pesticide resistance among insects The fittest phenotype may initially be rare But its frequency increases over multiple generations As the conditions continue to exist 3. Disruptive Selection = two or more extreme phenotypes are more fit Than the intermediate phenotype the snail ,..... or peppered Moth
Evolution Depends on Several Additional Things
Natural selection can only work on the traits that exist in the species or in the population And only on the traits that show The more varied the choices .... The more natural selection has to work with (compare to shopping, cloths, TVs)
Natural Selection = Survival of the Fittest
Natural selection is the driving force of evolution When environmental factors preserve favorable variations in a population And select out - or reject --- less favorable or harmful variations By differential reproductive success Natural Selection is occurring.. Natural selection is the process by which populations become adapted to their environment In evolution, -- by natural selection "The fitness of an individual is measured By how reproductively successful its offspring are In the next generation" The fitness of an individual is measured by how reproductively successful its offspring are in the next generation
Selective Breeding
Of what can happen in populations where breeding is not random The result is a wide variety of sub-populations Of dogs, cats, cattle, horses and all agricultural crops Where the differences We like..... Are maintained with human control of the breeding SELECTIVE BREEDING AND THE RESULTS Migration moves individuals into and out of various populations. Departing members of a population Take their alleles with them Incoming individual bring new alleles with them Migration can counteract the effects Of both natural selection and genetic drift By bringing in new genes and by increasing the numbers of alleles in the population The human populations were once isolated by geographic barriers Like mountain ranges, and large bodies of water These barriers restricted migration and kept gene pools separate isolated Giving rise to racial differences Kind of like we talked about with Gene Drift and the Amish
Heterozygous Advantage or Superiority
Often co-dominant or incomplete dominant genes. Q The environment can promote the maintenance of 2 different phenotypes. Due to opposing selective pressures E.G. - Sickle-Cell condition The presence of all 3 phenotypes in the population - normal, sickle cell, & sickle cell anemia - is an example
Natural Selection and Genetic Drift
Once you have two populations of a species Natural selection and genetic drift begin to affect both populations independently And differently.... Because the environmental pressures are different And, because the alleles if each population will be different Given time --- this may result in one or more reproductive barriers Allopatric species.... Species separated by a physical barrier Helps explain the clusters of closely related species Found in groups of islands The Galapagos Islands have similar species of tortoise Finches, lizards etc to each other And to the Continent of South America Based on DNA evidence of all these species -- They are closely related to each other And--- they are similar to the species -- Found along the west coast of South America Also, based on the DNA clock This speciation probably began about 2 million years ago The tortoises show some of their distinct differences in their shell shape On the dryer islands the tortoise is forced to reach up to feed on bushes For additional food And the shell is notched to allow them to do this On wetter islands -- where there is lots of plant material on the ground - - - the notch does not exist -- Because the pressure for its development does not exist These sub-species of tortoise often interbreed when they are transported to other islands So... either they have not been separated long enough to form distinct species - Or accidental movement of members of the different population of the sub-species Has prevented them from actually forming a true reproductive isolation
Embryonic Development Patterns Provide Evolutionary Clues
Recently the discovery of genes that contribute to development Has spawned the field of Evolutionary Developmental Biology Evo-Devo 1999 Because related organisms share many physical traits They must also share the systems that produce these traits. A good example is how a chimpanzee skull and a human skull Look a lot alike in the womb and when they are both young But by the time either is an adult - the skulls have developed In very different ways
Geological Time Scale --- There are two ways to date Fossils
Relative dating Method Absolute dating Method Relative Dating --- sediment layers contain fossils - - - Logically. . . The deepest layers should contain the oldest fossils Logic is only useful if you have all or most of the facts... Problems occur when something disturbs the layers It wasn't until the early 1800s that some scientists figured this out It was also at this time that researchers noticed . . . . That the fossils had a progression In general. . . the oldest fossils are in the oldest and deepest layers of sediment And were less complex than those in the more recent layers And... many of the organisms the fossils represented Had gone extinct --- no longer existed Relative dating places fossils in order... From oldest to most recent But - does not actually give a date about when they lived and died.
Evolution
Scientists agree that evolution has brought about the species diversity we see around us today And this evolution is best described as Descent with Modification Which means Within a population - some alleles of various traits Become more common generation after generation = over time Others --- less common or they disappear --- As reproduction occurs over generations This is a change in allelic frequencies ***
Natural Selection Does Not Have a GOAL
So, statements like . . . "The orchids started producing the sent (pheromones) because they needed to attract male wasps" Or "The orchids makd pheromones in order to trick wasps into pollination. . ." Evolution does not have a goal . . . The fact that the odor the orchids produce resembles the female wasp's pheromones Was a happy accident that - - - because it was working to increase pollination. . . It lead to the selective elimination of the orchids That did not quite mimic the odor closely enough And were therefore not pollinated as often So, fewer, and fewer offspring --- till only the orchids that had the sent Were left in the area This is an example of a Physiological Adaptation!!!
Non-Random Mating & Recombination
Species with random mating --- no courtship Every individual has an equal chance of mating And passing on their genetic information into the future. And since..... no two eggs are the same and no two sperm are the same No two offspring will be the same and the species will continue to change over time With only the best adapted surviving - and reproducing Examples include; plants that are wind pollinated Many primitive marine animals like sponges, corals, clams and oysters Animals that are mostly sessile Simply release sperm and eggs into the water Where the eggs are fertilized There are some species that swarm... like some squid and all fresh water eels But many species court.... And mating is NOT random The selection process means That individuals exhibiting the "preferred genes" Reproduce more often leaving more offspring
Homologous Structures
Structures that had the same evolutionary origin ... But may have a different function A bat's wings, and a mouse's front legs The front flippers of a whale and the limbs of a dog or a cat
Sympatric Speciation Occurs in a Shared Habitat
Sympatric speciation is a little harder to explain and a little harder to defend Part of the explanation is that just because a researcher Can't look at two areas in the same place And detect the differences Doesn't mean the differences don't exist And doesn't mean it won't have an effect on the species living there The books talks about two species of Chiclid fish like Tilapia Living in the same lake --- but in different location And utilize different resources . . . Reproducing in different areas... Maintaining sympatric, reproductive isolation
Bottlenecks are found in the U.S. too
The American bison was hunted almost to extinction - and The Greater Prairie Chicken has lost most of it habitat Things like this is one of the reasons Environmentalists attempt to Save all the Populations of species
At the Hardy-Weinberg Equilibrium Allele Frequencies do Not Change
The Hardy-Weinberg equilibrium is the unlikely situation In which allele frequencies and genotype frequencies do not change From one generation to the next Because Sexual reproduction will not in and of itself change the allelic frequency of a population The Hardy-Weinberg equilibrium can occur if and only if A population meets all 5 of the following criteria
LIFE ON EARTH - TIME LINE
The current rate of extinction is estimated to be 20-200 species/year/million species There are many factors causing this loss of species Loss and destruction of habitat is believed to be the major cause As the human population grows: cities expand, agriculture expands There are more roads and highways All of this fragments habitat - creating barriers to migration and other problems
The theory of Plate Tectonics and shifting Continents
The earth's surface consists of several rigid layers, Called tectonic plates They move in response to forces acting deep within the planet --- Where the plates smash into each other - - - Mountain ranges form. Sometimes one plate moves above another Forming a trench..... or a valley Because the 7 different Plates were connected or very close to each other over time Many plants and animals are found on many of the plates Based on migration and seed dispersal.
Macro evolution
The large complex changes in the life of the world. most common -- It usually occurs over a long period of time and many, many generations.
Sexual selection comes in two forms:
The members of one sex COMPETE with each other For access to the opposite sex; Q Here the opposite sex - usually females - do not chose & don't care The male must be the winner of the competition Eg; big horn sheep, seals, sea lions, African lions etc Or... One sex --- usually the females - chooses her mate From among the males that court her Probably includes humans???, penguins - gifts, best nest
Why does the female usually get to make the choice?
The point of pairing and sex is .... Offspring --- and In most cases females invest more into those offspring They produce the eggs, -- or the babies They spend more time rearing them than males do With mammals - females produce milk to feed the babies If all of this energy was used in competition for the male And in the production of bright coloration etc. Instead of in the production and care of the offspring Numbers and survival of the babies is likely to be compromised
HETEROZYGOTE ADVANTAGE
The sickle cell allele is common where malaria is common In regions where malaria thrives, the people that are heterozygous for the Sickle Cell Allele are the most likely to survive long enough to reproduce. And they have a 25% chance of producing a child that has Sickle Cell Child.
Embryology
The similarities and differences in the way a baby "what-ever" Develops in the womb or in the egg
There are several problems using Reproduction as the method to define species
There are several problems using Reproduction as the method to define species 1. This method can't be applied to organisms that only reproduce asexually Q Asexual organisms include all bacteria & Archaea, some Protista, some fungi etc. 2. It is impossible to apply this method to species that are extinct Since they will never have sex again...... 3. Some closely related species have the ability to interbreed Especially in captivity but would not do so in nature. 4. In some species the reproductive isolation is NOT absolute Some species of plants, for example, will occasionally produce fertile offspring together Eg. Coy-wolf. . . . . northern gray wolf
Genetic variation
Within a species (or Population) no two individuals are exactly alike. **Some of this variation can be inherited. This is not true with Asexual reproduction.
Seymouria
a reptile like amphibian These kinds of fossil records help us tell what arose 1st And what it gave rise to And the types of changes that were occurring That lead to all the plants and animals we see today
Eusteoptheon
amphibious fish
Species Distribution reveals Evolutionary Events
e Rise and Fall of the Marsupials Marsupials were once the most widespread mammals on earth They are primitive pouched mammals Where the young are born tiny, naked, and blind Helpless and very immature - - - almost embryonic Once born they must find their way into their mother's pouch And locate a nipple to feed By 110 MYA the placental mammals had evolved The young of placental mammals develop within the mother's body, Nourished and protected by her. They are born more fully developed than the marsupials. This gives them a better chance of survival after birth Placental mammals quickly replaced the marsupials Everywhere their populations overlapped For a time - - North and South America were separate land masses - - - With placental mammals in North America And marsupials in South America Then about 1 or 2 MYA a land bridge was laid down Between the two land masses From sediment eroding from both continents And placental mammals moved into South America And soon. . . most of the marsupials went extinct
Jean Baptiste Lamarck
in 1801 formulated the theory of "Acquired Inheritance"
HOW OLD IS THE EARTH?
in the 1700s and before --- (300 years ago and before) .... People thought the world was only about 6000 years old Only 100 years later most scientists thought the earth Was at least several million years old But..... that all life around us was as it had always been Today most scientists ... and most people Accept that the world is over 4.6 Billion years old This was determined by dating meteorites that have hit the earth over time An age of 4.55 ± 0.07 billion years, very close to today's accepted age, Was determined by Clair Cameron Patterson using uranium-lead isotope dating On several meteorites including the Canyon Diablo (AZ) meteorite and published in 1956 Both geologists and astronomers agree that the Earth is roughly 4.6 billion years old. Additional data was collected from soil and rock samples taken from the Moon And by additional dating methods as rubidium-strontium and uranium-lead The two oldest meteorites are calculated to be 4.4 & 4.5 Billion years old If the earth hadn't been here.... The meteorites could not have struck us These ages are further supported by determining the age of the moon. Which we think was created when a meteor struck the earth in such a way That a large chunk was dislodged - some of that chunk became the moon The age of the moon was determined from moon rocks Brought back from the Apollo 14 landing And the moon is about 60 million years younger than the earth.
Species
is a group of individuals or populations capable of interbreeding -- and producing fertile young. Speciation = the formation of a new species. And this occurs when some individuals can no longer successfully interbreed with the rest of the group. Speciation can occur . . . . If a population or members of a population Become Allopatrically = geographically-----Isolated From other populations of the same species Why Geographic Isolation? Intact interbreeding populations share a common gene pool Gene Pool = is all the alleles within a population In humans; all of our colors, blood types, hair types, handedness, genetic diseases, everything Once isolation of a population occurs Micro-evolution begins to occur in both populations This causes the genetic information of both populations to diverge - - - Remember gene Drift.....The founder effect and the Bottleneck effect Also, remember Weinberg's equilibrium and the fact that it is never met. Over time. . . there may be enough genetic divergence In the different gene pools To cause them to become reproductively isolated from each other - - - Human population... tremendous variation ... not separate species
Paleontology
is the study of fossil remains or other clues of the past Like foot prints and fossilized scat You remember that we said - - during Darwin's time scientists suspected That the Earth was hundreds of millions of years old But ..... no one knew how old. Again, we now know that the earth is 4.6 billion years old Fossils provide the original evidence for evolution Hinting at when species diverged from a common ancestor
Founder effect
occurs when a small group of individuals Separates off from its home population and establishes a new..... isolated population The alleles found in this sub-sample of the original population May not represent the alleles of the original population So --- a common gene may not occur at all And.... An uncommon one may become common Example; The Amish people of Pennsylvania Provide a famous example of the Founder Effect..... In the 1700s - - about 200 followers of the Amish faith Immigrated to North America from Switzerland One couple, carried the recessive allele associated with Ellis-Van Creveld Syndrome An autosomal recessive trait that causes a form of dwarfism Where limbs are short. . . . and there are extra fingers In Switzerland the occurrence of the trait was less than 1% Intermarriage in the small American population Brought the disorder to about 7% here
The Bottleneck Effect
occurs when population numbers drop radically Over a short period of time This Bottleneck causes the loss of many alleles That were present in the larger ancestral populations So, even if the few remaining individuals reproduce And the populations recovers to its original numbers There is a loss of genetic diversity that is permanent
Descent with Modification
over many generations --- natural selection will select for those traits that best succeed in getting the limited resources -- and will change the characteristics of populations --- even giving rise to a new species - - or at least a new race.
Archaeopteryx
shows both bird and reptile features They have both jaws and teeth, a long, bony, jointed tail Feathers and wings
Adaptation occurs in 3 ways
structural, behavioral and physiological And these changes can be learned and inherited Natural selection - requires preexisting genetic diversity Then, selectively eliminates individuals that are least able to compete For resources -- or cope with the prevailing environment
Unequal reproductive success (Natural Selection)
the inherited characteristics of some individuals make them more likely to obtain these resources, survive and reproduce in greater numbers.
Prezygotic Mechanisms
these methods prevent fertilization And usually exist in species that have been separated for a long time than the Postzygotic mechanisms There are 5 types 1. Habitat Isolation --- Habitat isolation occurs when habitat preferences lower the probability of mating between individuals associated with differing habitats. The species are in the same area but occupy different habitats. The European partridge and the chucker both occupy the rocky mountain side The partridge is an Alpine species and is never found below 3,000 feet The Chucker is never found above 3,000 feet These two species - simply never encounter each other. 2. Temporal Isolation - - - Species mate at different times; like seasons or times of the day. Brown trout mate in the fall, - - - Rainbow trout mate in the spring -- they never mate with each other. If a species of insects mate at dawn and a closely related species mates at dusk..... Red and Black sea urchins release gametes at different times of the year 3. Behavioral Isolation - - - Species respond to different courtship behaviors; Things like songs, calls, pheromones, displays or other signals. This is especially important in Birds, Amphibians, Fish and Insects. With carnivores...... it is truly a fine line between sex and violence Black widow spider. . . . scorpions 4. Mechanical Isolation - - - The sex organs are incompatible Most important in Plants But occurs with animals too
Many traits are neutral
until they are not. This allows them to stay in a population for a long time
Transitional links
which are fossils that help link groups together
Prezygotic Reproductive Isolation
which occurs before fertilization of the egg Habitat Temporal Behavioral Mechanical Gamete
We are diploid
with recessive traits that are only expressed when homozygous. Natural selection impacts the information expressed. It cannot impact what is not seen.
