The Theory of EvolutionThe process where organisms change

The Theory of Evolution-The process where organisms change over a period of time (a new species from previous species). Theories of evolution (process of change through time) attempt to explain the similarities and differences among species. A species is a group of organisms that look alike, can interbreed, and are capable of producing fertile offspring.

• Population: organisms of the same species living in the same place at the same time and compete for resources (food, water, etc) • Habitat: place where organism lives • Adaptation: any physical characteristic or behavior that helps an organism to better survive • Competition: interaction among organisms to better obtain resources or mating opportunities over others to survive • Overproduction: creating more offspring than the environment can support

• Reproductive success: passing on of genes to the next generation • Variation (genetic variation): differences in a specific trait found within a population • Struggle for existence: idea that organisms must compete and only the most fit with survive • Descent with modification (evolution): idea that all organisms share a common ancestor but that species change over time due to natural selection and better adaptations

• Darwin’s Theory: Natural Selection – Charles Darwin, an English scientist, took a voyage on a ship named the Beagle, which lasted five years. – He studied the local animals and plants on various islands and continents. Darwin noticed that each species seemed well adapted to its environment. – By studying fossils, he realized that some forms of life no longer existed. – After his voyage, Darwin wrote a book called On the Origin of Species by Natural Selection. This book presented a theory of evolution that totally changed biology. – Darwin used the data he gathered from the natural world to form his well-known idea of evolution by natural selection.

Best adapted to living in the water Best adapted to living in the air

• Darwin’s Theory was based on the presence of variation among members of a species and the process that he called “natural selection. ” • In Darwin’s theory, environmental pressures act as a force for the natural selection of the best adapted individuals—those with helpful adaptations that enable them to survive and reproduce successfully. According to Darwin, evolution occurs because of natural selection. The environment doesn’t dictate the changes, rather the environment dictates who will survive. He wanted to explain how species adapt to their environment over many generations.

• Introduction to Natural Selection: – Natural Selection: Way in which populations change as certain organisms reproduce and pass on their genes to future generations. » Natural selection is the survival and reproduction of the organisms, which are genetically best adapted to the environment. Light to attract prey Big mouth to catch prey

Natural Selection depends on 6 things: 1. All species have genetic variation 2. Overproduction: organisms create more kids than can survive in the environment 3. Struggle for existence: Competitions for survival (food, habitat, etc. ) 4. Adaptations: Survival of the fittest: Organisms that are better adapted to live long enough to produce more offspring than organisms that are not very well adapted. Traits (Dominant or Recessive) of best adapted organisms tend to become more frequent in the population. » Ex: Peppered Moths » Ex: Alligators live in the Everglades and make up a population because they all live together in a particular area and are able to reproduce. 5. Reproductive success: Organisms with less favorable variations are less likely to survive and pass on traits to the next generation. 6. Descent with modification: all organisms have a common ancestor but with natural selection, the traits best adapted to a certain habitat tend to become more common in a population

– Natural selection does NOT cause new traits; it favors traits already present that make an organism better able to survive. – Organisms interact in an area; this interaction leads to competition, and the organisms that are best adapted are going to live long enough to survive and produce offspring. They pass these traits to their offspring. Eventually, the traits better suited for survival become more common, and fewer individuals without the trait are produced. This is a genetic shift, which brings about speciation: the development of a new species.

Disease agents can effect survival with natural selection • Organisms/populations are more likely to survive if: – Resistant to disease – Have greater genetic diversity – Have Larger gene pool

Diversity in Gene Pools • Genetic Diversity the variety of traits; this makes organisms of the same species different from one another. • Mutations: random changes in DNA, are the only way to add new traits to a gene pool. which scientists believe caused the variety of life. Natural selection doesn’t cause new traits to form, but only picks the best traits of the choices given

• Traits are passed from generation to generation through genes, which are sections of DNA. The total number of genes that account for different traits in a species is called its gene pool. – Ex: Humans are very diverse. We have different hair color, skin color, & eye color; we have different heights & weights; we have different sizes & shapes of noses, eyes & ears; & we even have different personalities, intelligence, & talents. The different genes that account for all of these different traits make up the human gene pool

• Species that have a large gene pool have a greater diversity because they have more combinations of genes available to them. • A small gene pool limits a species’ diversity. • Gene pools of species can increase due to mutations, or it can decrease when traits die out. As a species becomes more specialized to a specific environment, it loses its ability to adapt to changes. Species can lose traits through natural selection, genetic drift, the threat of extinction, & selective breeding.

• Gene flow: movement of genes or alleles into or out of a population • Immigration: movement of an organism into a new population or location • Emigration: movement of an organism out of a population or location

• Genetic drift is the change in a gene pool generated by chance. – Ex: If a species of insect can have white or brown eyes, & both eye colors are equally beneficial & equally found in a population, then just because of chance, more offspring are born with brown eyes during one season. Because more of the population has brown eyes, the next generation will more than likely have brown eyes. Over time, the population drifts toward having more brown eyes than white eyes, & pretty soon, the gene for white eyes may be lost. • The threat of extinction or any drastic decrease in population size often accelerates genetic drift. The remaining organisms have a more limited gene pool. This new gene pool may favor a different trait than what was seen in the original population. When a small population repopulates, it results in what is called the founder effect.

• The bottleneck effect can occur when genetic drift happens due to a devastating event greatly reduces the population size and genetic diversity. • After 80% of a population of long-tailed mice were eliminated because of a hurricane, the remaining 20% survived & all belonged mostly to one closely related family. In this mice family, they have a genetic defect that causes them to have short stumpy tails instead of long tails. Because of the founder effect, the gene pool now contains a larger percentage of this genetic defect, which causes the trait to become more common in the new population.

3. Nature uses natural selection & genetic drift for determining genes that are passed on; however, human can use artificial selection through selective breeding. a. Farmers can select traits that make their crops more profitable & easily harvested. b. Through selective breeding, certain “undesirable” traits have been bred out of the gene pool. c. Because this has been done for many years with wheat, the crop that is now produced is almost genetically uniform with little variation. i. ii. Because wheat has little diversity, it may not be able to grow in different climates, & the lack of variation makes it susceptible to evolving diseases & pests. Mutations can add genetic variations. In stable environments, mutations may have little or no benefit, or they are likely to be harmful. In a changing environment, however, mutations may allow organisms to adapt.

Antibiotic and Pesticide Resistance on Gene Pools: • When people use antibiotics to kill bacteria, pesticides to kill bugs, and herbicides to kill weeds, eventually a bacteria, bug, or weed develops a genetic mutation that will make it immune to the killing chemical • This bacteria, bug, or weed will not die and then reproduces more with the same mutation • Now, the only bacteria, bugs, or weeds left will all be resistant to the killing agent!

Formation of a new SPECIES: – Speciation: formation of a new species as a result of divergent evolution – Speciation can occur when members of populations no longer interbreed – The original species before the changes is called the common ancestor – Factors effecting the rate (speed) of evolution: • • Population size (smaller evolves faster) Environment (changing environments evolve faster) Mutation rate (more mutations evolve faster) Reproduction rate (faster reproductive rate evolves faster)

• Evolution may take several paths that can ultimately lead to the formation of a new species from a single ancestral species; there are 3 patterns of evolution that lead to a new species: species may evolve apart (diverge), evolve similar structures and appearances (converge), or evolve together (coevolve). – Convergent Evolution – Pattern of evolution in which 2 or more unrelated species become more & more similar in appearance as they adapt to the same kind of environment, often resulting in analogous structures. • Ex: Whales & fish have similar characteristics since both had to evolve methods of moving through the same medium—water. – Divergent Evolution – Pattern of evolution in which 2 or more related species gradually become more dissimilar. • Ex: kit fox & red fox • Adaptive Radiation – ex. of divergent evolution; many related species evolved from a single ancestral species (**if an organism invades an area where there are few competing species & new habitats are available, new species will evolve) ex: finches – Coevolution – the joint change of two or more species in close interaction • Ex: predator & prey; parasite & host; plant-eating animal & the plants they feed on; pollination between plants & animals (bats & light-colored flowers)

Divergent Evolution: Pattern of evolution in which two closely related species gradually become more and more dissimilar. Convergent Evolution: Pattern of evolution in which two unrelated species gradually become similar to each other through adaptation to a common environment, often resulting in analogous structures Parallel Evolution: Pattern of evolution in which two species maintain the same degree of similarity while each undergoes changes along an independent path.

Types of Reproductive Isolations: • Reproductive isolation: causes speciation; inability of populations to interbreed due to some kind of barrier (physical, behavioral, etc) • Geographic Isolation –physical barrier divides a population into two or more separate groups –Subspecies: geographically isolated population of a species that has its own distinct characteristics but still capable of breeding within species –Ex: a volcano eruption separates islands. The populations have to adapt to their new environment. Over time each population may become a different species • Allopatric speciation: formation of a new species through geographic isolation

• Temporal (Reproductive) Isolation (TIME) » Different reproductive cycles (seasonal). Due to the species not being able to interbreed, they may become so different they can no longer interbreed. » Ex: Frogs live in the same areas. Some of the frogs mate during the Spring, while others mate during the Fall. These frogs don’t interbreed because of temporal isolation; eventually, these frogs may become so different they can no longer interbreed and are two separate species. –Mechanical Isolation: » Occurs due to differences in size, shape, and/or location of genitalia » Ex: two snail shells opening the opposite direction

• Behavioral Isolation: – A type of isolation between populations due to differences in courtship or other mating behaviors. – 2 populations will not interbreed because of different ritualistic behaviors. • Ex. 2 similar species of birds may overlap in territories and may be capable of producing fertile offspring, but because they sing a slightly different mating song, they will not interbreed in the wild.

• Natural selection can result in a species that is better ADAPTED to a particular environment. The individuals that produce the greatest number of offspring are the best adapted. – Adaptations are considered any trait, physical or behavioral, that helps the organism survive. – Natural selection acts on populations NOT individual organisms. It changes the frequencies of alleles, Tall vs. Short, etc. (peppered moth) Populations evolve, individuals don’t because natural selection operates only on populations over many generations. • EX: Albino deer will not survive long enough to reproduce. Therefore, each new generation is made up largely of offspring from parents with the most favorable variations. • Ex: The Peppered Moths in England were all gray with a few darker and black varieties. The gray moths blended in with the trees, so most of them survived, and the black moths were eaten by birds. After the industrial revolution, there was a lot of soot in the air that settled on the trees making them black. Today, in England most of the Peppered Moths are black, instead of gray. • Natural selection causes changes in the frequencies of alleles. In the moths, it was the same species of moth; however, the dark allele was more commonly expressed than the light allele.

3 types of Natural Selection: (in which the population is affected) • Stabilizing Selection – Natural selection favors average individuals • Ex: Insects: if too large, they may be eaten by birds; if too small, can’t find food. • Directional Selection: – Favors organisms with an extreme form of a trait • Ex: Finches: During drought food was scarce, the finches with larger beaks were able to find food as a result the average size of beaks increased • Disruptive Selection – Favors organisms with both extremes and eliminates the average. • Ex: If only very large seeds and very small seeds are available, then birds with large and small beaks would be best adapted, and the number of average size beaks would decrease.

• External Fertilization – Animals like fish produce very large numbers of egg and sperm and release them into the water – Large numbers are necessary because most eggs will not be fertilized and even the fertilized eggs don’t have a high survival rate. Most will die. • Internal Fertilization – Sperm and egg are more likely to fuse together and develop into an adult – Therefore, only small numbers of egg and sperm are needed because most will survive – This give animals with internal fertilization an advantage.

• Behavioral Adaptations – Elaborate mating rituals, ex: male peacock – Ritualistic fights among males to attract females – Hibernation: • Many animals that do not live in large groups to survive when the environment is not well suited for survival they hibernate. • The animal is not exposed to predators or the environment • Metabolism, including digestion, respiration, and heart rate, slows down – Estivation: • A resting state similar to hibernation that some animals use in hot weather (instead of cold weather for hibernation). Since reptiles and amphibians are ectothermic, they must still be able to survive even if the temperature surrounding them gets too hot. If the environment gets too hot or too dry, frogs & reptiles will estivate. • Estivation allows animals to conserve energy by slowing their respiration and heartbeat. These organisms will not require as much food or water to survive. • Some organisms, like reptiles, can use 90 -95% less energy when they are estivating.

Estivation Hibernation

– Migration: • The movement of an animal from one region or climate to another for a specific period of time. This is usually a seasonal travel to a more favorable environment. • Examples of migrating animals: hummingbirds, robins, ducks, sea turtles, elk, whales, & monarch butterflies – Social groups among animals are useful in helping find food and defend themselves. This is also a disadvantage because if there is a natural or environmental disaster, disease, etc. , then the entire group could be killed.

• Adaptations for protection against predators: – Protective coloring: • Camouflage is a structural adaptation that provides protection for an organism to blend in with its surroundings. Organisms that are well camouflaged are more likely to escape predators and survive to reproduce. – Ex: The coloration of flounder allows it to avoid predators. • Warning coloration is a type of protective adaptation in which the organism is venomous or toxic to other organisms. – Ex: Poison Dart Frogs in the rain forest use their bright colors to send a signal stating that they are poisonous. Yellow & red are colors that usually mean DANGER!

Camouflage

Warning Coloration

– Protective resemblance: • Mimicry is a structural adaptation that provides protection for an organism copying the appearance of another species that is potentially harmful. – Ex. The non-venomous king snake mimics the venomous coral snake. – Ex. The non-nasty viceroy butterfly mimics the nasty-tasting monarch butterfly. • Self-mimicry is a special kind of protective adaptation, whereby one part of an animal mimics another part of its body. – Ex. Insects have coloration that appears to be large eyes to scare off predators. – Ex. Some insects display self-mimicry when their anterior & posterior regions look alike.

Mimicry Self-mimicry

• Plant Adaptations – Seed dispersal in angiosperms (flowering plants) • Wind, like dandelions or maples • Hooks, like hitchhikers • fleshy fruits, like apples, so that animals can eat them and disperse them through their feces – Without dispersal, then the offspring would fall close to the parent plant and would compete for sun, water, nutrients, etc.

• If organisms are not suited for their survival, they could become endangered or extinct giving way for the better suited organisms. – Extinction leads to species replacement. • Over long periods of time, events, such as climate changes and natural disasters, result in some species becoming extinct, which means that they disappear permanently. Species that are better suited to the new conditions may replace those that became extinct. • Ex: The extinction of dinosaurs was followed by the evolution of modern mammals and birds over millions of years.

• Populations continually change due to the following: – Overpopulation—There are more offspring produced because of good conditions. Soon enough, however, there are too many. – Competition—Due to problems, certain populations compete with each other. – Survival of the fittest—The ones better suited to the environment will survive. – Natural Selection—A mechanism that explains how populations evolve. – Reproduction—Individuals that survive will reproduce. – Speciation—The process in which new species form.

Speciation Survival of the Fittest Overpopulation Competition Reproduction Natural Selection