Evolution and Darwin

Evolution is surrounded by controversy Why? People have religious beliefs People don’t like the idea that “Human’s came from monkeys” There is a lot more to evolutionary theory than monkeys.

The Camps surrounding Evolutionary Theory Creationists- believe a supreme being (God, Allah, Great Spirit etc.) created everything as it is today Intelligent Design-followers believe the living world is too complex for it to just happen. Some intelligent form had to be behind making the blue prints. Evolutionists- believe organisms changed over time to their present forms.

What do you need to do to be successful with Unit #4? You do not have to believe Evolutionary Theory. You only have to understand its principals and concepts that we learn in our future lessons

Old Theories of Evolution Jean Baptiste Lamarck (early 1800’s) proposed: “The inheritance of acquired characteristics” He proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.

“The Inheritance of Acquired Characteristics” Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

Would these acquired characteristics get passed on to their offspring? Of course not. The acquired characteristics did not cause changes in the sex cells

Larmarck’s Theory Use and Disuse -Fish in caves don’t use their eyes so they disappear -Elephants use their trunks a lot so they get longer Although false, his theory was the first attempt to explain how organisms adapted to their environment over time

Charles Darwin Influenced by Charles Lyell who published “Principles of Geology”. This publication led Darwin to realize that natural forces gradually change the Earth’s surface and that the forces of the past are still operating in modern times.

Charles Darwin Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. On the Galapagos Islands, Darwin observed species that lived nowhere else in the world. These observations led Darwin to write a book.

HMS Beagle and its route

California Academy of Sciences in San Francisco Mr. Down’s spent the day there on a summer trip to visit my son and daughter The CAS had an incredible Darwin Exhibit

You will use this chart for Beaks of Finches Lab

Darwin’s Finches

Charles Darwin Wrote in 1859: “On the Origin of Species by Means of Natural Selection” Two main points: 1. Species were not created in their present form, but evolved from ancestral species. 2. Proposed a mechanism for evolution: NATURAL SELECTION

Natural Selection Individuals with favorable traits are more likely to leave more offspring better suited for their environment. Also known as “Differential Reproduction” Example: English peppered moth (Biston betularia) - light and dark phases

Artificial Selection The selective breeding of domesticated plants and animals by man. Selective Breeding is also called Artificial selection Question: What’s the ancestor of the domesticated dog? (Canis familiaris) Answer: WOLF (Canis lupus)

Mr. Downs’ dog Clancy at 6 weeks old

Both of these trees are in my yard and are the same species (Thuja occidentalis) Which one looks better? Why? They are both in the same environment (water, sun, nutrients are the same). Why do they look so different? Different Traits in their DNA Which one do you think humans selected desirable traits in deliberate plant crosses? A B

Darwin is the founder of Modern Evolutionary Theory Science attempts to: -Describe events based on phenomena we can observe -Explain events of the past in terms of events we can observe today -Make predictions about future events  

A Theory such as Evolution Theory is supported by a lot of data collected by thousands of Scientists Theories can be discarded (i.e.Lamarck) or revised as scientist get new information Theories can’t be proven with absolute certainty (i.e.-Gravitational Theory, Cell Theory, Contagious Disease, Genetics)

Darwin is the founder of Modern Evolutionary Theory Evolution is the processes that have transformed life on earth from it’s earliest forms to the vast diversity that characterizes it today. Evolution results in A change in the genes!!!!!!!!

Darwin never did claim that humans originated from monkeys. Darwin claimed that humans and monkeys (well, apes really) have a COMMON ancestor. That is, they originated from the same species many years ago

Evolution is the process (mutation, adaptation, natural selection and extinction) of change in a population through generations Existing life forms have evolved from earlier life forms. Evolutionary theory is a unifying principle for the biological sciences. ( Genetics, Biochemistry, Anatomy, Physiology etc.)

Evolution Theory provides an explanation for the differences/ similarities in structure, function, and behavior among life forms.

Evidence of Evolution Cladograms or phylogenetic trees are graphic representations of species relationships. Common Ancestor

Evidence of Evolution 1. Geographical distribution of species. Alfred Russell Wallace was also known as the "father of biogeography. Biogeography -the study of the past and present geographical distribution of organisms. Reproductive Isolation- prevents mating with birds on the other islands. Two populations develop independently

2. Fossil Record: Fossils and the order in which they appear in layers of sedimentary rock (strongest evidence). Younger Fossils Older Fossils

Evolution of the horse What changes do you notice in moving from the bottom to the top? Increase in size Changes in the leg bones

Relative Dating-In relative dating, something is determined to be older or younger than something else by using the laws of superposition. -Layers (strata) close to the surface are younger -Deeper Layers contain the oldest strata Absolute Dating-dating determines the actual age of artifacts -One of the most widely used and well-known absolute dating techniques is carbon-14 dating, which is used to date organic remains.

Evidence of Evolution 3. Taxonomy-classification of organisms into different categories based on their physical characteristics and presumed natural relationships (remember Did King Philip Come Over………..?) In 1735, Carolus Linnaeus published a book in which he outlined his scheme for classifying organisms and is still in use today The Linnaean system uses two Latin name categories, genus and species , to designate each type of organism.

4. Homologous structures: Structures that are similar because of common ancestry (comparative anatomy)

Homologous Structures- structures shared by related species because they have been inherited from a common ancestor. (flipper of a whale and hand of a human) Analogous Structures- Analogous structures serve the same function in different species but is not a result of sharing a common ancestor. (wing of a butterfly and wing of a bird) Vestigial Structures- organ or structure that once was useful in an animal’s evolutionary past, but that now is useless or very close to useless. (wing of an ostrich)  

My favorite Vestigial Structures Whale Snake

Plica Semilunaris -it is the “crusty” factory Plica Semilunaris -it is the “crusty” factory. It secretes a sticky mass that collects any foreign materials. All this trash is surrounded by the sticky gook so that it does not scratch the sensitive cornea.

Darwin’s point is found in the majority of mammals, and humans are no exception. It is most likely used to help focus sounds in animals, but it no longer has a function in humans. Wisdom Teeth - Early humans ate a lot of plants – and they needed to eat them quickly enough and eat a sufficient amount in one day to get all of the nutrients they needed.

Evidence of Evolution 5. Comparative embryology: Study of structures that appear during embryonic development. Any ideas on why the embryos are so similar? Scientist believe that mutations at early stages result in death or spontaneous abortion.

6. Molecular biology: DNA and proteins (amino acids) Diagram shows chromosome 1 next to the human chromosome 1. The A-T bases are black and the G-C bases white. Blue areas in the rendered chromosomes identify bases not known yet. DNA Analysis can show us how closely related different organisms are.

-There is no thought involved in Natural selection -There are no choices in Natural Selection -It is all about the genes an organism is born with

Concepts of Natural Selection 1. Overproduction -- Within a population, more offspring are born than can possibly survive.   These are tadpoles that hatched from one female toad. Do you think many will survive?

2. Competition – Over production results in struggle for space, water, food, light, mates or other limited resources   3. Variations-Members of populations show variations (differences in traits) that make certain individuals better adapted to survive

4. Natural Selection-Some variations are more helpful than others, there is a natural selection against organisms that can’t adapt.   5. Organisms that can’t adapt DIE and some populations may become extinct

6. Survival of the Fittest -- The individuals who survive are the ones best adapted. 7. Inheritance of variations-Organisms with helpful variations survive and live long enough to REPRODUCE. 8. The best adapted individuals survive and reproduce, passing on the favorable variations to their offspring (& population ). These changes improve the fitness of a species (population) in its environment

9. If an organism does not live long enough 9. If an organism does not live long enough to reproduce it has NO EFFECT ON THE EVOLUTION OF THE POPULATION. 10. Individuals can’t evolve, only populations can evolve. (make sense because genes have to be passed on to offspring for evolution to take place. 11. Evolution of New Species-Over long periods of time, so many variations may accumulate that a population may become a new species. This process is called Speciation  

Some Sources of Variation in Modern Natural Selection Theory 1. The genetic basis for variation within a species is provided by mutations and sexual reproduction. (crossing over and recombination)   2. Mutations are spontaneous and provide the raw material for evolution.

Modern Natural Selection Theory 1.) All species have the potential to increase in numbers. 2.) There is a finite amount of resources for any species. Species tend to make too many organisms for these resources. 3.) Species will show genetic variability due to mutation, crossing over, and genetic recombination (during fertilization) of genes. 4.) The scarce finite resources of the environment will select those offspring better able to survive and less fit offspring may die.

5.) Variations within a species increases the likelihood that at least some members of the species will survive under changed environmental conditions. -Traits which are beneficial to the survival of an organism in a particular environment tend to be retained and passed on, and therefore, increase in frequency within a population. -Traits which have a low survival value to organisms tend to diminish in frequency from generation to generation. -If environmental conditions change, traits that were formerly associated with a low survival value may, in a changed environment, have greater survival value and increase accordingly.  

Population Genetics The science of genetic change in population. Hardy-Weinberg equation is important and will be discussed shortly.

Vocabulary Population- A localized group of individuals belonging to the same species. Species- A group of populations whose individuals have the potential to interbreed and produce viable offspring. Gene Pool-The total collection of genes in a population at any one time.

Hardy-Weinberg Principle The concept that the shuffling of genes that occur during sexual reproduction, by itself, cannot change the overall genetic makeup of a population.

Hardy-Weinberg Principle This principle will be maintained in nature only if all five of the following conditions are met: 1. Very large population 2. Isolation from other populations 3. No net mutations 4. Random mating 5. No natural selection

Hardy-Weinberg Principle Remember: If these conditions are met, the population is at equilibrium. This means “No Change” or “No evolution”. The Hardy–Weinberg equilibrium is impossible in nature. Genetic equilibrium is an ideal state that provides a baseline to measure genetic change against.

Macroevolution The origin of taxonomic groups higher than the species level. Involves very long periods of time Grand scale changes in organism Scientists can see changes in fossils of Intermediate species Sea cow (manatee) ancestor with legs

Microevolution A change in a population’s gene pool over a secession of generations. Evolutionary changes in species over relatively brief periods of geological time.

Five Mechanisms of Microevolution 1. Genetic drift: Change in the gene pool of a small population due to chance. Two examples: a. Bottleneck effect b. Founder effect

a. Bottleneck Effect Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces population size. (result are similar to inbreeding) Examples of disasters: 1. Earthquakes 2. Volcano’s 3. Droughts

b. Founder Effect Genetic drift resulting from the colonization of a new location by a small number of individuals. Founder populations are often found on islands Results in random change of the gene pool. Mutiny on the Bounty (1789): Population of 9 mutineers, 8-9 Tahitian females and 6 Tahitian males to uninhabited Pitcairn Island.  

Five Mechanisms of Microevolution 2. Gene Flow: The gain or loss of alleles from a population by the movement of individuals or gametes. Immigration- movement out/away Emigration- movement in

Five Mechanisms of Microevolution 3. Mutation: Change in an organism’s DNA that creates a new allele. 4. Non-random mating: The selection of mates other than by chance. 5. Natural selection: Differential reproduction- competition for mates, those best adapted survive and produce more offspring.

Modes of Action Natural selection has three modes of action: 1. Stabilizing selection 2. Directional selection 3. Diversifying selection Number of Individuals Size of individuals Small Large

1. Stabilizing Selection Acts upon extremes and favors the intermediate. Number of Individuals Size of individuals Small Large

2. Directional Selection Favors variants of one extreme. Number of Individuals Size of individuals Small Large

3. Diversifying Selection Favors variants of opposite extremes. Number of Individuals Size of individuals Small Large

Speciation The evolution of new species.

Reproductive Barriers Any mechanism that impedes two species from producing fertile and/or viable hybrid offspring. Different species most likely have different number of chromosomes Two barriers: 1. Pre-zygotic barriers 2. Post-zygotic barriers

1. Pre-zygotic Barriers a. Temporal isolation: Breeding occurs at different times for different species. b. Habitat isolation: Species breed in different habitats. c. Behavioral isolation: Little or no sexual attraction between species.

1. Pre-zygotic Barriers d. Mechanical isolation: Structural differences prevent gamete exchange. e. Gametic isolation: Gametes die before uniting with gametes of other species, or gametes fail to unite.

2. Post-zygotic Barriers a. Hybrid inviability: Hybrid zygotes fail to develop or fail to reach sexual maturity. b. Hybrid sterility: Hybrid fails to produce functional gametes. c. Hybrid breakdown: Offspring of hybrids are weak or infertile.

Interesting but not Fertile Lion- 38 Tiger- 38 Horse- 64 Donkey- 62 Mule- 63 Human - 46 Chimpanzees- 48 Gorilla- 48

Allopatric Speciation Induced when the ancestral population becomes separated by a geographical barrier. Example: Grand Canyon and ground squirrels

Adaptive Radiation Emergence of numerous species from a common ancestor introduced to new and diverse environments. Example: Darwin’s Finches

Sympatric Speciation Result of a radical change in the genome that produces a reproductively isolated sub-population within the parent population (rare). Example: Plant evolution - polyploid A species doubles it’s chromosome # to become tetraploid. reproductive sub-population Parent population

Interpretations of Speciation Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime. 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change.

Convergent Evolution Species from different evolutionary branches may come to resemble one another if they live in very similar environments. Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert)

Coevolution Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species. Example: 1. Acacia ants and acacia trees 2. Humming birds and plants with flowers with long tubes

Speciation-creation of new species Morphology-study of structure Geographic Isolation (Reproductive Isolation)- Divergent Evolution- Convergent Evolution Coevolution- Adaptive Radiation- Genetic Drift-

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