Evolution: Unit 1 2025 PDF

Unit 1: Evolution and Biodiversity What is Evolution? Phylogenetic Trees Evolution of Populations...

Unit 1: Evolution and Biodiversity What is Evolution? Phylogenetic Trees Evolution of Populations Origin of Species History of Life Biodiversity: Bacteria, Archaea, Protists, Fungi & Plants The Tree of Life/ The Phylogeny of Life Spring 2025 Show and tell 2  Today’s Topic: Evolution- Descent with modification (Ch. 22)  Synopsis for today (1) Understand patterns in biodiversity (2) Explain natural selection and artificial selection (3) Understand evolution Evolution: descent with modification Key points from today’s lecture (1) The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species. (2) Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life. (3) Evolution is supported by overwhelming evidence, including the fossil record, homologies, direct observations, and molecular (DNA) data. What Is Biodiversity? “Biological diversity, often shortened to biodiversity, is the variation of life at all levels of biological organization, referring not only to the sum total of life forms across an area, but also to the range of differences between those forms. Biodiversity runs the gamut from the genetic diversity in a single population to the variety of ecosystems across the globe.” -- Center for Biological Diversity https://www.biologicaldiversity.org/programs/biodiversity/elements_of_biodiversity/index.html 6 7  Soil Biodiversity & Human Health “Soil biodiversity is often negatively affected by the interaction between poor land management practices and drivers of climate change, both of which ultimately compromise ecosystem function and services that are essential for human health (control of pests and pathogens, production of nutritious food, cleansing water and reducing air pollution). Responses to reduced human health can in turn affect management decisions that govern land use and climate change.” Wall et al. (2015) Nature 528:69-76  Observations About Biodiversity Rich biodiversity in nature Pattern of shared characteristics Organisms suited for life in their local environments Variations in: Body size Bill size Bill shape Diet (conifer seeds) Vocalizations Crossbill Birds: Example 9  Observation About Biodiversity Shared characteristics among different species illustrate the unity of life Different species also have differing characteristics – For example, mantis species differ in size, shape, and color Quick and Dirty Tip What is Evolution? Evolution happens to populations, not individuals. Evolution is not directed towards a goal.  What Is Evolution? Change in the genetic composition (allele frequencies) of a population from generation to generation Variation in a trait(s) Population: Smallest size that can evolve Time/Temporal Emperor Penguins Note: Individuals do not evolve! Multiple generations are pictured above 12  What Is Evolution? Evolution can be viewed as both a pattern and a process –Pattern is revealed by scientific data showing that life has evolved over time –Process consists of the mechanisms that cause the pattern of change  Evolution: Fact or Fiction? Natural selection can cause population change (via allele frequency change) over time. - Fact Written human history as well as geological record, records changes in types of organisms over time - Fact Change of allele frequency over time leads to changes in phenotypic frequencies over time - Fact The mechanisms of evolution in different events are still in contention. Specific histories of specific organisms may be controversial. 14  EVOLUTION Evolution is a fact The general mechanisms are well-established Mechanisms are still being studied & debated New models of how Evolution can work beyond traditional views (Nat. Sel.) are known and studied Evolution and Religion/Spirituality are NOT mutually exclusive. One is open to study by science, the other through study by faith. Origins of Evolutionary Theory Plato (427-347 BCE) Unchanging linear ladder of life. Human are on top of the ladder. 16 Aristotle (384-322 BCE)  Origins of Evolutionary Theory Plato and Aristotle – Species are immutable & unchanging – Focus on interspecific variation Plato (427-347 BCE) Natural theology (1700s-1800s) – Discover the Creator’s plan by studying nature – Linnaeus (1707-1778) – binomial nomenclature 17 Aristotle (384-322 BCE)  Origins of Evolutionary Theory Georges Cuvier (1769-1832) – paleontologist – Extinctions have occurred (unique fossils in each stratum) – Catastrophism – successive creations, not evolution James Hutton (1726-1797); Charles Lyell (1797-1875) – geologists – Gradualism – gradual changes can accumulate – Uniformitarianism – same processes acting today 18  Origins of Evolutionary Theory Fossils of extinct taxa are in a consistent order in the strata. 19  Origins of Evolutionary Theory Darwin (1809-1882) – Influenced by geologists (Hutton, Lyell) Earth is very old (4.6 billion > 6000) Slow processes over long time → substantial change Darwin Species evolve Malthus’s economics – population growth Lamarck 20  Origins of Evolutionary Theory: Lamarck Individuals match their environment Traits change due to use and disuse Characteristics acquired during lifetime are passed to offspring Organisms have a drive to be more complex Individuals do not evolve! Individuals do not decide to change to Chinese elm (Ulmus parvifolia) “get stronger” or “reproduce more”! 21 Voyage of the Beagle (1831-1836) 22  Galápagos Finches Observable Pattern: varied beak shapes match food source Inferred Process: beak shapes are inherited adaptations that promote survival & reproduction (fitness); i.e., natural selection for individuals that possess such traits 23 What Is Fitness? Fitness is the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals. The fittest individual (the organism with the highest fitness) is the one who has the greatest percentage of alleles in future generations. Note: Individuals who die young but reproduce a lot while alive can have high levels of fitness! 24 Adaptations Inherited traits that help an individual survive and reproduce (enhance fitness) Salt-limiting Gland Oil-secreting Gland Streamlined Body Webbed Feet Blue-Footed Booby 25 Descent With Modification Where on the tree is the common ancestor of elephants and hyraxes? Which species are extinct? Which species are extant?  Natural Selection: Darwin 1. Traits of individuals in populations often vary. 2. Traits are inherited from parents to offspring. 3. Species can produce more offspring than the environment can support. 4. Since resources are limited, many offspring die. 27  Inferences From Darwin’s Theory Peppered moth - Biston betularia 1. Individuals who inherit traits that provide a higher likelihood of survival and reproduction in a given environment tend to leave more offspring than other individuals. 2. This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over time. 28  Natural Selection African wild dog Coyote Wolf Fox Jackal Thousands to millions of years of natural selection Ancestral canine Five Species of Canines 29  Evolution by Natural Selection Five Species of Canines African wild dog Coyote Wolf Fox Jackal 1. Traits vary in population Thousands to = Evolution by Nat. Sel. millions of years 2. Traits are inherited from parents to offspring of natural selection 3. Individuals differ in reproductive output Ancestral canine  Artificial Selection Share the same wolf common ancestor How does artificial selection differ from natural selection? How are artificial and natural selection similar? 31  Natural Selection: Key Points Defined as: the differential survival and reproduction of individuals carrying alternate inherited characteristics. 1. Individuals DO NOT evolve!!!! Populations are the smallest size that evolve over time. 2. Natural selection only acts on HERITABLE traits Characteristics acquired during an individual’s lifetime are not heritable. 32  Natural Selection: Key Points 3. Favorable traits depend on the ENVIRONMENTAL CONTEXT Environmental conditions vary spatially and temporally so favorable traits are context specific. 4. Natural selection is not goal-oriented Don’t say: Polar bears evolved white fur in order to sneak up on prey. Do say: White fur was selected for in the ancestor of polar bears because it increased fitness. If the environment changed and white fur was no longer adaptive (i.e. no more snow!), the environment/evolution/polar bears could not “make” the fur change to a different color (without the necessary genetic mutations….more on that later!) 33 Is this statement correct? “Lions evolved big teeth in order to kill and eat big prey.”  There is no “goal” toward which natural selection is working, only differential survival and reproduction of individuals carrying alternate inherited characteristics Thus, please DO NOT say things like, “Lions evolved big teeth in order to kill and eat big prey.” Instead, think…. Big teeth became a predominant trait in lion populations because they conferred increased fitness Variation in teeth already existed and Nat. Sel. Favored increased size in the pop. Do antibiotics cause bacteria to become resistant? Explain your response. Environmental Change & Evolution What happens over time when the soapberry bug’s food resources change? Note: Evolution does not require Balloon vine (native to a changing environment to occur. Florida) Changing environments can impact evolution, but the environmental change is not required for evolution to happen. 38  Environmental Change & Evolution Balloon vine (native Goldenrain tree (native to Asia) to Florida) - Recently introduced to Florida - Population size has - Strong population size decreased - Seeds located closer to surface - Seeds buried deeper How would you explain the change in average beak length using natural selection? 39  Theory of Evolution What is a “theory”? Evidence for evolution: Observed facts: The pattern of species differences; characters that are shared. Hypothesized, testable mechanisms: The processes of evolution: natural selection as the means of change. Together, these patterns and successful predictions generated from our understanding of processes form the theory of evolution. Scientific theories are rigorously tested unifying concepts rather than hypotheses (“educated guesses”) Theories still leave room for further study and clarification: Evolution is known to occur, but some aspects have been clarified over time (e.g., punctuated equilibria and inclusion of processes such as sexual selection, genetic drift, gene flow) Evolution is the unifying theory of all of biology 41 Evolution: descent with modification Key points from today’s lecture (1) The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species. (2) Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life. (3) Evolution is supported by overwhelming evidence, including the fossil record, homologies, direct observations, and molecular (DNA) data. (more on this next week) Next: The Evolution of Populations & Origin of Species