EVOLUTION Part I Change Over Time Misconception Evolution

  • Slides: 57
Download presentation
EVOLUTION Part I: Change Over Time

EVOLUTION Part I: Change Over Time

Misconception: “Evolution is a theory about the origin of life. ” • Response: Evolutionary

Misconception: “Evolution is a theory about the origin of life. ” • Response: Evolutionary theory deals mainly with how life changed after its origin. Science does investigate how life started, but this is not the central focus of evolutionary theory. Most studies of evolution are focused on the branching and diversifying AFTER it started.

Misconception: “Evolution is ‘just’ a theory. ” • Response: Scientific theories are explanations that

Misconception: “Evolution is ‘just’ a theory. ” • Response: Scientific theories are explanations that are based on lines of evidence, enable valid predictions, and have been tested in many ways. In contrast, there is also a popular definition of theory—a “guess” or “hunch. ” These conflicting definitions often cause unnecessary confusion about evolution.

What is Evolution? • The processes that have transformed life on earth from it’s

What is Evolution? • The processes that have transformed life on earth from it’s earliest forms to the vast diversity that characterizes it today. A change in the genes over time!! (What does this mean? What will cause this? ) MUTATIONS!

Charles Darwin • Darwin read a publication (by Charles Lyell) that talked about how

Charles Darwin • Darwin read a publication (by Charles Lyell) that talked about how natural forces gradually change Earth’s surface. • He wondered if this type of gradual change applied to living organisms…

CHARLES DARWIN, cont. • In 1831, he signed on as a naturalist for a

CHARLES DARWIN, cont. • In 1831, he signed on as a naturalist for a 5 year expedition that sailed to the Galapagos Islands (off west coast of South America). • On the trip, he collected huge numbers of plant and animal specimens • Noticed there was tremendous diversity in the organisms he observed • From this experience, Darwin developed The theory of natural selection

Voyage of the Beagle

Voyage of the Beagle

Galapagos Islandsof Ecuador off coast

Galapagos Islandsof Ecuador off coast

Darwin’s theory of natural selection • Darwin hypothesized: • organisms look different because their

Darwin’s theory of natural selection • Darwin hypothesized: • organisms look different because their environments are different. • differences allow each species to survive in its particular environment. • Example: the firefly beetle “glows” to attract a mate, insuring the survival of the species • Example: the vegetarian finch has a beak best suited to eating buds and fruit; an insect-eating finch has a different beak SURVIVAL OF THE FITTEST!!!

Chapter 7 Section 3 Natural Selection in Action

Chapter 7 Section 3 Natural Selection in Action

DARWIN’S FINCHES

DARWIN’S FINCHES

Charles Darwin • In 1859, he wrote: wrote • “On the Origin of Species

Charles Darwin • In 1859, he wrote: wrote • “On the Origin of Species by Means of Natural Selection” Two main points in the article: 1. Species were not created in their present form, but evolved from ancestral species. 2. He proposed that NATURAL SELECTION is the mechanism for evolution

4 Main points of Natural Selection 1. There is variation within a population (we

4 Main points of Natural Selection 1. There is variation within a population (we NOW know this is based on CHANGES in the genes- mutations!) 2. Some variations are favorable 3. Not all young produced in each generation can survive 4. Individuals that survive and reproduce are those with favorable variations

How does Natural Selection work? • Individuals with favorable traits are more likely to

How does Natural Selection work? • Individuals with favorable traits are more likely to have and leave more offspring better suited for their environment • THAT is how a population of organisms adapts to their environment!

Which variation is favorable? What will the next generations look like? • w

Which variation is favorable? What will the next generations look like? • w

Misconception: “Natural selection involves organisms ‘trying’ to adapt. ” • Response: Natural selection leads

Misconception: “Natural selection involves organisms ‘trying’ to adapt. ” • Response: Natural selection leads to adaptation, but the process doesn’t involve “trying. ” Natural selection involves genetic variation and selection among variants present in a population. Either an individual has genes that are good enough to survive and reproduce, or it does not—but it can’t get the right genes by “trying. ”

What does “survival of the fittest” really mean? • The fittest member of a

What does “survival of the fittest” really mean? • The fittest member of a population is the individual that is MOST successful in its environment AND produces the most offspring…passes on the most copies of its genes.

What are Selective Pressures? • Factors that result in selection of specific variations/phenotype: 1.

What are Selective Pressures? • Factors that result in selection of specific variations/phenotype: 1. Predation 2. Changes in climate or other environmental factors (food, water, etc) 3. Disease 4. Competition for food, space, reproductive resources …survival means passing on genes.

Important Points of Evolution: v Individuals do not evolve: populations evolve v Natural selection

Important Points of Evolution: v Individuals do not evolve: populations evolve v Natural selection can amplify or diminish only heritable traits; acquired characteristics cannot be passed on to offspring v Evolution is not goal directed and does not lead to perfection; favorable traits vary as environments change Copyright © 2009 Pearson Education, Inc.

Scientists observe natural selection in action: Rosemary and Peter Grant have worked on Darwin’s

Scientists observe natural selection in action: Rosemary and Peter Grant have worked on Darwin’s finches in the Galápagos for over 20 years – In wet years, small seeds are more abundant and small beaks are favored – In dry years, large strong beaks are favored because large seeds remain http: //www. hhmi. org/biointeractive/origin-species-beakfinch Copyright © 2009 Pearson Education, Inc.

Natural selection in action, cont. Development of pesticide resistance in insects – Initial use

Natural selection in action, cont. Development of pesticide resistance in insects – Initial use of pesticides favors those few insects that have genes for pesticide resistance – With continued use of pesticides, resistant insects flourish and vulnerable insects die – Proportion of resistant insects increases over time MRSA & other antibiotic resistant bacteria - Methicillin Resistant Staphylococcus Aureus - Many cases of Staph infections involve this strain; may have occurred because of overuse of antibiotics. Copyright © 2009 Pearson Education, Inc.

Chromosome with allele conferring resistance to pesticide Additional applications will be less effective, and

Chromosome with allele conferring resistance to pesticide Additional applications will be less effective, and the frequency of resistant insects in the population will grow Pesticide application Survivors

Why doesn’t natural selection reduce genetic variation in populations by retaining only the most

Why doesn’t natural selection reduce genetic variation in populations by retaining only the most favorable genes (alleles)? Diploidy preserves variation by “hiding” recessive alleles – A recessive allele is only subject to natural selection when it influences the phenotype in homozygous recessive individuals – For example, cystic fibrosis Copyright © 2009 Pearson Education, Inc.

Natural selection cannot fashion perfect organisms 1. Selection can only act on existing variation

Natural selection cannot fashion perfect organisms 1. Selection can only act on existing variation – Natural selection cannot conjure up new beneficial alleles 2. Evolution is limited by historical constraints – Birds arose as the forelimb of a small dinosaur evolved into a wing Copyright © 2009 Pearson Education, Inc.

Wing claw (like dinosaur) Long tail with many vertebrae (like dinosaur) Teeth (like dinosaur)

Wing claw (like dinosaur) Long tail with many vertebrae (like dinosaur) Teeth (like dinosaur) Feathers

Natural selection cannot fashion perfect organisms, cont. 3. Adaptations are often compromises 4. Chance,

Natural selection cannot fashion perfect organisms, cont. 3. Adaptations are often compromises 4. Chance, natural selection and the environment interact Copyright © 2009 Pearson Education, Inc.

Artificial Selection • The selective breeding of domesticated plants and animals by man. •

Artificial Selection • The selective breeding of domesticated plants and animals by man. • Question: What’s the ancestor of the domesticated dog? • Answer: WOLF

Evidence of Evolution 1. Fossil Record: Fossils and the order in which they appear

Evidence of Evolution 1. Fossil Record: Fossils and the order in which they appear in layers of sedimentary rock (strongest evidence). Which is older- lower or higher in the rocks? 2. Homologous structures: Structures that are similar because of common ancestry (comparative anatomy)

Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat

Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat

Evidence of Evolution 3. Molecular biology: Sequence comparison of DNA and proteins (amino acids)

Evidence of Evolution 3. Molecular biology: Sequence comparison of DNA and proteins (amino acids) 4. Taxonomy: Classification of life forms- how they compare & relate to other organisms.

 • http: //www. pbs. org/wgbh/nova/evolution/ guess-embryo. html

• http: //www. pbs. org/wgbh/nova/evolution/ guess-embryo. html

Patterns of descent are shown on an evolutionary tree The sequence of branching on

Patterns of descent are shown on an evolutionary tree The sequence of branching on an evolutionary tree is determined by homologous structures (fossil &/or anatomical) and genes (DNA seq data). Each branch point (# on the following tree) represents the common ancestor of all species that descended from it. Evolutionary trees are hypotheses that reflect current knowledge of patterns of evolutionary descent Copyright © 2009 Pearson Education, Inc.

Evolutionary Tree of Tetrapods Lungfishes Amniotes Mammals 2 Tetrapod limbs Amnion Lizards 3 and

Evolutionary Tree of Tetrapods Lungfishes Amniotes Mammals 2 Tetrapod limbs Amnion Lizards 3 and snakes 4 Crocodiles Ostriches 6 Feathers Hawks and other birds Birds 5 Tetrapods Amphibians 1

Phylogenies are based on homologies in fossils and living organisms Phylogeny: evolutionary history of

Phylogenies are based on homologies in fossils and living organisms Phylogeny: evolutionary history of a species or group of species Hypotheses about phylogenetic relationships can be developed from various lines of evidence – The fossil record provides information about the timing of evolutionary divergences – Homologous morphological traits, behaviors, and molecular sequences also provide evidence of common ancestry Copyright © 2009 Pearson Education, Inc.

Species: Felis catus Genus: Felis Family: Felidae Order: Carnivora Class: Mammalia Phylum: Chordata Kingdom:

Species: Felis catus Genus: Felis Family: Felidae Order: Carnivora Class: Mammalia Phylum: Chordata Kingdom: Animalia Bacteria Domain: Eukarya Archaea

Order Family Genus Species Felidae Felis catus (domestic cat) Mephitis Lutra Mustelidae Carnivora Mephitis

Order Family Genus Species Felidae Felis catus (domestic cat) Mephitis Lutra Mustelidae Carnivora Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis Canidae Canis latrans (coyote) Canis lupus (wolf)

Shared characters are used to construct phylogenetic trees A phylogenetic tree is a hypothesis

Shared characters are used to construct phylogenetic trees A phylogenetic tree is a hypothesis of evolutionary relationships within a group Cladistics uses shared derived characters to group organisms into clades, including an ancestral species and all its descendents Shared ancestral characters were present in ancestral groups Copyright © 2009 Pearson Education, Inc.

Shared characters are used to construct phylogenetic trees An important step in cladistics is

Shared characters are used to construct phylogenetic trees An important step in cladistics is the comparison of the ingroup (the taxa whose phylogeny is being investigated) and the outgroup (a taxon that diverged before the lineage leading to the members of the ingroup) – The tree is constructed from a series of branch points, represented by the emergence of a lineage with a new set of derived traits – The simplest hypothesis is the most likely phylogenetic tree Copyright © 2009 Pearson Education, Inc.

CHARACTERS TAXA Iguana Duck-billed platypus Kangaroo Beaver Long gestation Iguana 0 0 0 1

CHARACTERS TAXA Iguana Duck-billed platypus Kangaroo Beaver Long gestation Iguana 0 0 0 1 Duck-billed platypus Hair, mammary glands Gestation Hair, mammary glands 0 0 1 Kangaroo 1 Gestation 0 1 1 Beaver 1 Long gestation Character Table Phylogenetic Tree

Iguana Duck-billed platypus Kangaroo Beaver CHARACTERS TAXA Long gestation 0 0 0 1 Gestation

Iguana Duck-billed platypus Kangaroo Beaver CHARACTERS TAXA Long gestation 0 0 0 1 Gestation 0 0 1 1 Hair, mammary glands 0 1 1 1 Character Table

Build A Cladogram!

Build A Cladogram!

Shared characters are used to construct phylogenetic trees The phylogenetic tree of reptiles shows

Shared characters are used to construct phylogenetic trees The phylogenetic tree of reptiles shows that crocodilians are the closest living relatives of birds – They share numerous features, including fourchambered hearts, singing to defend territories, and parental care of eggs within nests – These traits were likely present in the common ancestor of birds and crocodiles Copyright © 2009 Pearson Education, Inc.

Iguana Duck-billed platypus Hair, mammary glands Kangaroo Gestation Beaver Long gestation Phylogenetic Tree

Iguana Duck-billed platypus Hair, mammary glands Kangaroo Gestation Beaver Long gestation Phylogenetic Tree

Lizards and snakes Crocodilians Pterosaurs Common ancestor of crocodilians, dinosaurs, and birds Ornithischian dinosaurs

Lizards and snakes Crocodilians Pterosaurs Common ancestor of crocodilians, dinosaurs, and birds Ornithischian dinosaurs Saurischian dinosaurs Birds

An organism’s evolutionary history is documented in its genome Molecular systematics compares nucleic acids

An organism’s evolutionary history is documented in its genome Molecular systematics compares nucleic acids or other molecules to infer relatedness of taxa – Scientists have sequenced more than 100 billion bases of nucleotides from thousands of species The more recently two species have branched from a common ancestor, the more similar their DNA sequences should be The longer two species have been on separate evolutionary paths, the more their DNA should have diverged Copyright © 2009 Pearson Education, Inc.

Mutations • Mutations are random changes in the DNA (genes) of an organism. •

Mutations • Mutations are random changes in the DNA (genes) of an organism. • Most mutations are unfavorable… occasionally, they may be beneficial and lead to evolutionary changes.

Adaptations • Inherited characteristics that helps an organism to survive and reproduce. • Are

Adaptations • Inherited characteristics that helps an organism to survive and reproduce. • Are the result of evolution by natural selection • Giraffe… neck • Peacock… flamboyant feathers • Bacteria… resistance to antibiotics • Human…?

Why/how did the giraffe get such a long neck? • Explain this using what

Why/how did the giraffe get such a long neck? • Explain this using what you have learned about natural selection (the 4 points).

4 Main points of Natural Selection 1. An early giraffe was born with a

4 Main points of Natural Selection 1. An early giraffe was born with a longer neck…. . (a CHANGE in her genes- a mutation!) 2. This giraffe was able to reach the higher, more plentiful leaves on the tree. 3. Many of her siblings with shorter necks did not survive. 4. She survived and had more offspring than other giraffes (& many of them had longer necks!).

Gene Pool • The total collection of genes in a population at any one

Gene Pool • The total collection of genes in a population at any one time. • Indicates diversity and genetic possibilities for the population.

To summarize: Mutation allows Adaptation leads to Speciation the process of evolution!

To summarize: Mutation allows Adaptation leads to Speciation the process of evolution!

Gradualism • Small genetic changes occur slowly within a population • Darwin originally proposed

Gradualism • Small genetic changes occur slowly within a population • Darwin originally proposed that evolution occurred at a slow, gradual rate

Punctuated equilibrium • 1972 - Stephen Jay Gould and Niles Eldridge • Populations stay

Punctuated equilibrium • 1972 - Stephen Jay Gould and Niles Eldridge • Populations stay stable for long periods of time, interrupted by brief periods of rapid change • Environmental change; increased mutation rate • Supported by fossil record

Gradualism vs Punctuated Equilibrium

Gradualism vs Punctuated Equilibrium

 • http: //glencoe. mheducation. com/olcweb/c gi/pluginpop. cgi? it=swf: : 550: : 400: :

• http: //glencoe. mheducation. com/olcweb/c gi/pluginpop. cgi? it=swf: : 550: : 400: : /sites/ dl/free/0078802849/383939/gradualism_P unctuated_Equilibrium. swf: :