BIOL171 Evolution And Origin Of Species F2024 PDF

Chapter 18 Evolution and Origin of Species BIOL 171 Introductory Biology 1 Luria Namba, Ph.D. Hawai’i Community College Learning Objectives Define evolution and natural selection Describe various evidence for evolution Define sp...

Chapter 18 Evolution and Origin of Species BIOL 171 Introductory Biology 1 Luria Namba, Ph.D. Hawai’i Community College Learning Objectives Define evolution and natural selection Describe various evidence for evolution Define species, gene pool and speciation Describe how speciation can take place with or without geographic separation (Allopatric speciation vs sympatric speciation)  What’s Evolution? Darwin called evolution as “descent with modification” Species change over time Species: A group of similar organisms that can interbreed to produce fertile offspring. Species give rise to new species All species share the common ancestor (“Tree of Life”)  Natural Selection Charles Darwin and Alfred Wallace suggested that the mechanism of evolution is natural selection (“survival of the fittest”). When…. Traits are inherited Available resources are limited Variation exists among individuals in a population Offspring with traits that best compete for the limited resources will survive and reproduce more. Heritable traits that help organisms compete better become more common in a population over time. → Descent with modification What are some examples? (Complete the homework!) Adaptation Natural selection causes populations to become adapted to their environments over time. Populations become increasingly well-suited (increased “fit”) to their environments over time. Key Points about Natural Selection Natural selection is driven by the environment, resulting in adaptation Variation in traits are results of random mutation There are always more offspring than the environment can support (Overproduction of offspring) ○ Individuals with favorable traits will leave more offspring in the next generation Natural selection acts on existing heritable variation → ○ Over generations, the population will become adapted to its environment as the favorable traits become more predominant Evidence for Evolution 1. Fossils 2. Anatomy and embryology 3. Biogeography 4. Molecular biology 5. Direct observation of small-scale evolution Fossils Fossil records provide snapshots of the past, and successions of organisms through the tree of life through time. Radiometric dating is used to estimate the age of the fossils. Anatomy: Homology Homologous structures are parallel structures in diverse organisms and indicate shared ancestry (a common ancestor) Vestigial structures have no apparent function, but appears to be remnants of functional structures of the ancestors Anatomy: Convergent Evolution Analogous structures may evolve independently in species in similar environments by the process of convergent evolution Divergent versus Convergent Evolution Divergent evolution is a process where different species arise from a common ancestor Convergent evolution is a process where distantly related species develop similar structures as a result of adaptations Embryology Embryonic structures are very similar across species! Biogeography Each continents and geographically isolated places (e.g. Hawaii) has its own distinctive collection of plants and animals, with extensive diversities within the species. Geographic distribution of species supports the idea that species can exist and evolve only in geographic areas that were colonized by their ancestors. Molecular Homology: e.g. Hox genes Hox genes are a group of evolutionary conserved genes found in many organisms. Hox genes have been duplicated and evolved. Evolution in Action Eg. pesticide and antibiotic resistance BT resistant moth Methicillin-resistant Staphylococcus aureus COVID19 ○ COVID19 evolution Misconception about Evolution 1. Individuals evolve 2. Evolution explains the origin of life 3. Organisms evolve on purpose Checkpoinit What is natural selection? Use your own words. Can an individual organism evolve in its own lifetime? Why? What is the difference between homologous structure and analogous structure? Give an example. Learning Objectives ✓ Define evolution and natural selection ✓ Describe various evidence for evolution Define species, gene pool and speciation Describe how speciation can take place with or without geographic separation (Allopatric speciation vs sympatric speciation)  Biological Species A species is a group of individuals that actually or potentially interbreed in nature. (Exception: organisms that reproduce only or mainly asexually) An offspring from a cross between two species is a hybrid.  Population and Gene Pool A group of individuals of the same species living within a specific area is called the population. A population share a gene pool, a collection of all the genetic variations (i.e. alleles) in that population. Speciation Speciation is the formation of new species from one original species. Speciation can occur by geographic separation of populations (allopatric speciation: allo-= “other”) or from a population remaining in one location (sympatric speciation: sym-= “same”). Allopatric Speciation In allopatric speciation, isolation of populations lead to speciation. Allopatric speciation occurs when members of a species disperse to a new geographical area (dispersal) or separated geographically by a natural event. Eg. stickleback in Alaska Adaptive Radiation Members of a population disperses and find different niches or habitats Adaptations from this dispersal result in adaptive radiation E.g. honeycreepers, fruit flies, snails in Hawaii  Allopatric Speciation Which situation would most likely lead to allopatric speciation? A. Flood causes the formation of a new lake. B. A storm causes several large trees to fall down. C. A mutation causes a new trait to develop. D. An injury causes an organism to seek out a new food source. Why do island chains provide ideal conditions for adaptive radiation to occur? Sympatric Speciation Sympatric speciation is a process of speciation without geographic separation. Sympatric speciation occurs because two groups are no longer able to interbreed. This is called the reproductive isolation. ○ Eg. Anole lizard Reproductive Isolation Reproductive isolation may result from unable to carry out mating or fertilization (prezygotic barrier) or production of non-viable or sterile offspring (postzygotic barrier). Examples of prezygotic barriers are: Incompatible breeding schedule (Temporal isolation) Incompatible mating behavior (Behavioral isolation) Habitat isolation Incompatibility of reproductive structures or gametes Examples of postzygotic barriers are: Inability to produce viable or fertile offsprings due to a genetic incompatibility  Reproductive Isolation Which situation is not an example of a prezygotic barrier? A. Two species of turtles breed at different times of the year. B. Two species of flowers attract different pollinators. C. Two species of birds display different mating dances. D. Two species of insects produce infertile offspring.  “A Monkey Is More Evolved Than a Mouse” Is this statement True? Why or Why not? Explain.  Homework on Darwin and Wallace movie “Making of a Theory” Course Evaluation Survey (hawaii.edu/ces): Extra Credit