EVOLUTION Part I Change Over Time Misconception Evolution
- Slides: 57
EVOLUTION Part I: Change Over Time
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 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 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 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 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
Galapagos Islandsof Ecuador off coast
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
DARWIN’S FINCHES
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 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 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
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 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. 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 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 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 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 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 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 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) Feathers
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. • 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 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
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
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 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 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: Animalia Bacteria Domain: Eukarya Archaea
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 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 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 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 0 0 1 1 Hair, mammary glands 0 1 1 1 Character Table
Build A Cladogram!
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
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 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. • 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 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 you have learned about natural selection (the 4 points).
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 time. • Indicates diversity and genetic possibilities for the population.
To summarize: Mutation allows Adaptation leads to Speciation the process of evolution!
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 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
• http: //glencoe. mheducation. com/olcweb/c gi/pluginpop. cgi? it=swf: : 550: : 400: : /sites/ dl/free/0078802849/383939/gradualism_P unctuated_Equilibrium. swf: :
- Common misconception about evolution
- A misconception resulting from incorrect reasoning
- Hans burgerhof
- The canadian flag is red and white. cierto falso
- Types of migration
- How do communities change over time
- Continents change position over time
- The gradual change in a species over time
- Examples of pejoration
- Coevolution
- A gradual change in a community over time.
- It is a process of change through time
- Change in hereditary features over time
- Gradual change
- Why do classification systems change over time?
- Start time, end time and elapsed time
- Over the mountain over the plains
- Siach reciting the word over and over
- Taking over navigational watch
- To mix ingredients by gently turning one part over
- Parallel running implementation
- Change over delay
- Section 16-2 evolution as genetic change
- Industry evolution and strategic change
- Slow evolution
- Part whole model subtraction
- Unit ratio definition
- Part part whole
- What is a technical description?
- Bar layout design
- The part of a shadow surrounding the darkest part
- Minitab adalah
- Examples for physical change
- Chemical change and physical change
- Absolute change and relative change formula
- What is an integer
- Is rocket fuel burning a physical change
- A change in supply vs a change in quantity supplied
- Supply and demand curve shifts
- Enagic founder
- Reactive change is change that
- Physical and chemical changes examples
- Spare change physical versus chemical change
- Rocks change due to temperature and pressure change
- Whats the difference between a chemical and physical change
- How does a physical change differ from a chemical change
- What is an example of physical change
- First order of change
- Is chopping firewood a physical or chemical change
- Climate change 2014 mitigation of climate change
- Starbucks publicity
- Alteration in various aspects of society over time
- Pompeii logo
- How have attitudes towards immigrants changed
- The gradual development of a community over time
- Real self vs actual self
- World superpowers over time
- How to calculate speed with time and distance