Evolution Natural Selection Theory What is a theory

Evolution Natural Selection

Theory ► What is a theory? § A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world. ► Theory of evolution § Evolution is the process by which modern organisms have descended from ancient organisms. Species has changed over time.

Charles Darwin Born Feb. 12, 1809 Joined Crew of HMS Beagle, 1831 Naturalist 5 Year Voyage around world Avid Collector of Flora & Fauna Astounded By Variety of Life

Voyage of the Beagle In 1831, Darwin set sail from England aboard the H. M. S. Beagle for a voyage around the world. Darwin returned 5 years later in 1836

Observations During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time. ► He observed many plants and animals were well suited to the environments they inhabited. Darwin was puzzled by where different species lived and did not live.

Darwin's Observations Living Organisms and Fossils Darwin collected the preserved remains of ancient organisms, called fossils. Some of those fossils resembled organisms that were still alive. Others looked completely unlike any creature he had ever seen.

Darwin's Observations The Galápagos Islands Darwin observed that the Galápagos Islands were close together but had very different climates. Copyright Pearson Prentice Hall

The Journey Home Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galápagos.

Tortoises

The Journey Home Darwin wondered if animals living on different islands had once been members of the same species. These separate species would have evolved from an original South American ancestor species.

Those that helped Darwin’s idea Hutton and Lyell both geologists (Earth millions of years old. ► Hutton § 1795 published theory about geological forces that have shaped Earth. § Layers of rock form slowly. § Mountains formed from sea floor ► Lyell § Gave Darwin book Principles of geology § Scientists must explain past events that have shaped the earth. § Made Darwin think if the earth can change over time what about life?

Lamarck’s Theory of Evolution ► Idea called Law of Use and Disuse ► If a body part were used, it got stronger ► If body part NOT used, it deteriorated 13

Lamarck’s Theory of Evolution ► Inheritance Of Acquired Traits § Traits Acquired During Ones Lifetime Would Be Passed To Offspring 14 Clipped ears of dogs could be passed to offspring!

Lamarck’s Mistakes ►Lamarck Did NOT Know how traits were inherited (Traits are passed through genes) ►Genes Are NOT Changed By Activities In Life ►Change Through Mutation Occurs Before An Organism Is Born 15

Thomas Malthus ► What was Malthus' theory of population growth? § 1798 observed that babies were being born faster than people were dying. § Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.

Publication of On the Origin of Species ► He shelved his manuscript for years and told his wife to publish it in case he died. ► In 1858, Alfred Wallace sent an essay to Darwin for review. Wallace’s ideas summarized Darwin’s work. ► In 1859, Darwin published his book, On the Origin of Species.

In his book… ► Proposed a mechanism for evolution called natural selection. ► Presented evidence that evolution has been taking place for millions of years—and continues in all living things. ► Artificial selection is the selection by humans for breeding of useful traits from the natural variation among different organisms.

► https: //www. youtube. com/watch? v=x. Ol 0 t. H VV 6 Ck

The Struggle for Existence ► Darwin realized that high birth rates and a shortage of life's basic needs would force organisms to compete for resources. ► How is natural selection related to a species' fitness?

Survival of the Fittest ► The ability of an individual to survive and reproduce in its specific environment is fitness. ► Darwin proposed that fitness is the result of adaptations. ► An adaptation is any inherited characteristic that increases an organism's chance of survival.

Natural Selection ► Because of its similarities to artificial selection, Darwin referred to the survival of the fittest as natural selection. ► In natural selection, the traits being selected contribute to an organism's fitness in its environment.

Natural Selection ► Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species' fitness in its environment. ► Natural selection is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species ►

Descent with Modification ► Natural selection produces organisms that have different structures, establish different niches, or occupy different habitats. ► Each living species has descended, with changes, from other species over time. ► Darwin referred to this principle as descent with modification.

5 parts to natural selection ►Overproduction ►Competition ►Variations ►Adaptations ►Speciation

Overproduction ► Most species produce far more offspring than can possibly survive. ► Each year a female sea turtle lays over 100 eggs. ► Why isn’t the sea full of sea turtles?

Competition ► Since food and other resources are limited, the offspring must compete with each other to survive. ► Only a few turtles will survive long enough to reproduce.

Variation ► Crossing-over increases the number of genotypes that can appear in offspring. ► Sexual reproduction produces different phenotypes, but it does not change the relative frequency of alleles in a population.

Adaptation ► Some organisms are better adapted to their environment. ► Fitness – the ability of an individual to survive and reproduce in its environment due its traits ► Survival in nature – live long enough to pass genes on to offspring. ► Traits that make organisms successful are passed to the next generation

Speciation ► a new species is created when enough time has passed ► over time, variations that make a species successful accumulate ► Eventually, the entire species is different than it was.

Evolution of a Population ► A population is a group of individuals of the same species that interbreed. ► A gene pool consists of all genes, including all the different alleles, that are present in a population. ► The relative frequency of an allele is the number of times the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur.

Genetic variation ► In genetic terms, evolution is any change in the relative frequency of alleles in a population. ► The two main sources of genetic variation are mutations and the genetic shuffling that results from sexual reproduction.

Mutation ► A mutation is any change in a sequence of DNA. ► Mutations occur because of mistakes in DNA replication or as a result of radiation or chemicals in the environment. ► Mutations do not always affect an organism’s phenotype.

Populations NOT individuals ► Natural selection affects which individuals survive and reproduce and which do not. ► Evolution is any change over time in the relative frequencies of alleles in a population. ► Populations, not individual organisms, can evolve over time.

Peppered Moth ► The Industrial Revolution began in England in the late 1700 s. ► Smoke from the factories blackened the tree trunks of trees. ► Light colored moths were no longer camouflaged. ► What color was more suited for the new environment?

More on Speciation ► Speciation is the formation of new species. ► A species is a group of organisms that breed with one another and produce fertile offspring.

How do New Species Form? ► Geographic Isolation ► Continental Drift ► A new species may form when a group of individuals remains separated from the rest of its species long enough to evolve different traits. § A group is separated from the rest of the species

Video ► Darwin

Evidence of Evolution • 1. The fossil record • 2. Comparative anatomy • Homologous structures • 3. Similarities in early development, or embryology.

Fossil Record ► A fossil is the preserved remains or traces of an organism that lived in the past. ► A fossil can be formed from parts of live organisms, foot prints, or burrows left in mud. ► Actual age of fossils is determined by radioactive dating

Fossils ► Ice preservation ► Tar pit ► Tree sap hardens to form amber. ► Imprint fossils ► Cast fossils ► Mineralized fossils

video ► Fossil ► https: //www. youtube. com/watch? v=l. IEo. O 5 Kd. Pvg

► Most fossils are found in sedimentary rock – formed when water flows over land, ► Carrying the sediment (and whatever life form) into a body of water. ► Over time pressure turns the sediment into rock, preserving what’s inside.

Comparative Anatomy ► Similar body parts show an evolutionary relationship ► Homologous Body Structures – same bone structure but different functions. ► Vestigial Organs – organs or traces of organs that serve no purpose. ►Example: Humans: appendix, tailbone, wisdom teeth, and Goosebumps

Homologous Body Structures – same bone structure but different functions.

Similarities in early development, or embryology ► The study of embryos and their development ► The similarities suggest an evolutionary relationship among all vertebrate species.

Speed of evolution 2 theories ► Gradualism- Described as a slow ongoing process by which one species changes to a new species ► Punctuated Equilibrium - One species suddenly changes to another.

Graphs showing time frame of Evolution: ►Gradualism: # S P E C I E S ► Punctuated Equilibrium Time # S P E C I E S Time

video ► clip

Relation and common descent ► All living organisms are related to one another. ► Common descent – all species – living and extinct – were derived from common ancestors. ► Humans did NOT evolve from apes. ► We have a common ancestor that was neither human nor ape.

► Common Ancestor: all living organisms have a common ancestor and all life can be traced back to one original cell. ► From there life become diverse ► Common ancestor mean that living things can be traced back to a common relative. ► Example: Humans did not evolve from Apes but had a common ancestor with them 5 to 8 million years ago.

Branching Trees: Cladograms ► A branching tree is a diagram that shows how scientists think different groups of organisms are related.

Practice questions ► 1. A species of bird known as Bird of Paradise has been observed in the jungles of New Guinea. The males shake their bodies and sometimes hang upside down to show off their bright colors and long feathers to attract females. Females usually mate with the “flashiest” males. These observations can be used to support the concept that (1) unusual courtship behaviors lead to extinction ► (2) some organisms are better adapted for asexual reproduction ► (3) homeostasis in an organism is influenced by physical characteristics ► (4) behaviors that lead to reproductive success have evolved ►

► 2. Agriculturists have developed some varieties of vegetables from common wild mustard plants, which reproduce sexually. Which statement best explains the development of these different varieties of vegetables? (1) Different varieties can develop from a single species as a result of the recombination of genetic information. ► (2) Different species can develop from a single species as a result of the effect of similar environmental conditions. ► (3) Mutations will occur in the genes of a species only if the environment changes. ► (4) Variations in a species will increase when the rate of mitosis is decreased. ►

► 3. Even though identical twins have the same genetic material, they may develop slightly different characteristics because ► (1) each twin receives different chromosomes from the egg ► (2) one twin may only have genes from the father ► (3) gene expression may be influenced by factors that switch genes on and off ► (4) a gene mutation may have occurred before the zygote divide

► 4. Which statement concerning the evolution of species A, B, C, D, and E is supported by the diagram below? (1) Species B and C can be found in today’s environments. ► (2) Species A and D evolved from E. ► (3) Species A and C can still interbreed. ► (4) Species A, B, and E all evolved from a common ancestor and all are successful today. ►

► 5. Young birds that have been raised in isolation from members of their species build nests characteristic of their species. This suggests that the nest-building behavior is ► (1) genetically inherited from parents ► (2) learned by watching members of their species ► (3) a disadvantage to the survival of the species ► (4) a direct result of the type of food the bird eats

► 6. Which statement provides evidence that evolution is still occurring at the present time? ► (1) The extinction rate of species has decreased in the last 50 years. ► (2) Many bird species and some butterfly species make annual migrations. ► (3) New varieties of plant species appear more frequently in regions undergoing climatic change. ► (4) Through cloning, the genetic makeup of organisms can be predicted.

► 7. When a species includes organisms with a wide variety of traits, it is most likely that this species will have ► (1) a high proportion of individuals immune to genetic diseases ► (2) a greater chance to survive if environmental conditions suddenly change ► (3) less success competing for resources ► (4) limitless supplies of important resources, such as food and water

9. Some evolutionary pathways are represented in the diagram below. An inference that can be made from information in the diagram is that ► (1) many of the descendants of organism B became extinct ► (2) organism B was probably much larger than any of the other organisms represented ► (3) most of the descendants of organism B successfully adapted to their environment and have survived to the present time ►