Warm-Up Questions How old is the Earth? How long ago did life originate on Earth? What did the first life-forms look like? How long ago did dinosaurs go extinct? How long ago did human beings appear on Earth?

Warm-Up Questions How did life emerge on Earth? How do we know what organisms lived in the past? What is the theory of evolution? What is natural selection? What is artificial selection? What does “survival of the fittest” mean?

Evolution and Biodiversity: Origins, Niches, and Adaptations What is Evolution? Chapter 5

Key Concepts Origins of life Evolutionary processes Ecological niches Species formation Species extinction

Earth: The Just-Right, Adaptable Planet During the 3.7 billion years since life arose, the average surface temperature of the earth has remained within the range of 10-20oC What other conditions make life on Earth possible?

Origins of Life Evidence suggests that life on earth developed in 2 phases: Chemical Evolution and Biological Evolution Chemical Evolution formation of the Earth’s crust and atmosphere evolution of the biological molecules necessary for life evolution of the systems of chemical reactions needed to produce living cells (protocells)

H2O CH4 Electrode N2 CO2 NH3 H2 Condenser Cold water H2O Water vapor Electrode N2 CO2 NH3 H2 Electrical sparks simulating lighting provide energy to synthesize organic compounds Condenser Cold water Cooled water containing organic compounds H2O Sample for chemical analysis

Origins of Life http://www.youtube.com/watch?v=iahBQolXQH8 https://massasoit.instructure.com/courses/346438/wiki/video-the-primordial-soup-with-julia-child

Origin of life (3.6–3.8 billion years ago) Modern humans (Homo sapiens) appear about 2 seconds before midnight Recorded human history begins ¼ second before midnight Age of mammals Age of reptiles midnight Insects and amphibians invade the land Origin of life (3.6–3.8 billion years ago) Plants invade the land First fossil record of animals Plants begin invading land noon Evolution and expansion of life

History of the Earth Calendar First living cells - April 1st, 6pm Algae & Marine Invertebrates - November 26th, 4:24am Arthropods, Mollusks, first fish - December 1st, 6:36am Many fish, trilobites, vascular plants - December 5th, 7:42am Age of fishes, first amphibians, first insects - December 7th, 4:24am Mosses, many amphibians, first reptiles - December 13th, 6pm First mammals and dinosaurs - December 16th, 10:14pm Age of Dinosaurs, first birds - December 19th, 1:03am Flowering plants, mass extinction - December 23rd, 5:54am Birds and mammals flourish - December 28th, 1:09am Hominids, ice ages, giant mammals - December 31st, 9:09pm

How Do We Know Which Organisms Lived in the Past? Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis

Comparing Anatomy and Embryology Homologous Structures Parts that are similar in structure but different in function Humans, penguins, alligators, bats all have the same bones in their arms but they are used for different things

Comparing Anatomy and Embryology Analogous Structures Parts that are similar in function but not structure Ex: wings of bee, bird, bat

Comparing Anatomy and Embryology Similar Embryos Embryos of different (but related) organisms are very similar and have similar structures early on Must have similar proteins at work

Comparing Anatomy and Embryology Vestigial Structures Structures that are so reduced in size of function that they are merely traces of similar organs in other species Ex: tailbone and appendix in humans

Fossils Mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items provide physical evidence of organisms Fossil record is INCOMPETE

Fossils "It isn't easy to become a fossil… Only about one bone in a billion, it is thought, becomes fossilized. If that is so, it means that the complete fossil legacy of all the Americans alive today – that's about 310 million people with 206 bones each – will only be about 50 bones, one-quarter of a complete skeleton. That's not to say, of course, that any of these bones will ever actually be found. Bearing in mind that they can be buried anywhere within an area of slightly over 9.3 million square kilometers, little of which will ever be turned over, much less examined, it would be something of a miracle if they ever were” ~ Bill Bryson

Origins of Life Biological evolution change in the genetic makeup of a population of a species in successive generations, if continued long enough it can lead to the formation of a new species How do new genes get into the population? mutations, genetic drift (organisms coming in and out of the population) Populations – NOT INDIVIDUALS – evolve

Evolution and Adaptation Theory of Evolution – all species descended from earlier, ancestral species. HOMER Macroevolution - long-term, large-scale evolutionary changes through which new species are formed from ancestral species and other species are lost through extinction

Evolution and Adaptation Microevolution - small genetic changes that occur in a population Genes mutate, individuals are selected and populations evolve Gene pool – set of all genes in the individuals of the population of a species Mutation – changes in the structure or number of DNA molecules in a cell Mutations are random, rare, only source of totally new alleles Exposure to mutagens Mistakes during replication

Evolution and Adaptation Natural selection Process in by which individuals of a population acquire genetically based traits that increase their chances of survival and their ability to produce offspring Adaptation (n.) A heritable trait that enables an organism to better survive and reproduce under a given set of environmental conditions Artificial selection Humans select one or more desirable genetic traits in the population of a plant or animal

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

Natural Selection Conditions necessary for natural selection: Variability – phenotypic differences in a trait Heritability – trait must have a genetic basis to evolve Differential Reproductive Success – phenotypic traits determine individual survival and success Combination of survival and reproduction is called “fitness” Fig. 5-4 p. 96 CD ANIMATION 4

3 Types of Natural Selection Stabilizing Selection Individuals with the average form of a trait have the highest fitness Represents the optimum for most traits Results in a similar morphology between most members of the species Directional Selection Individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait A shift in one direction Peppered moth Diversifying Selection Individuals with either extreme variation of a trait have greater fitness than individuals with the average form of the trait A shift in both direction, away from the center Shell color (dark rocks and light sand)

Warm-Up What is the difference between stabilizing, directional, and diversifying natural selection?

Directional Natural Selection Snail coloration best adapted to conditions Average New average Previous average Natural selection Number of individuals Number of individuals Average shifts Coloration of snails Coloration of snails Proportion of light-colored snails in population increases

Stabilizing Natural Selection Light snails eliminated Dark snails eliminated Natural selection Snails with extreme coloration are eliminated Number of individuals Number of individuals Coloration of snails Coloration of snails Average remains the same, but the number of individuals with intermediate coloration increases

Diversifying Natural Selection Intermediate-colored snails are selected against Snails with light and dark colors dominate Natural selection Light coloration is favored Dark coloration is favored Number of individuals Number of individuals Coloration of snails Coloration of snails Number of individuals with light and dark coloration increases, and the number with intermediate coloration decreases

Evolution Primers Isn't Evolution Just a Theory??? How Does Evolution Really Work? How Do We Know Evolution Happens?

Limits on Adaptation Through Natural Selection A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce Humans have a relatively slow generation time (decades) and output (number of offspring) versus some other species

Common Myths about Evolution through Natural Selection Misconception #1: Survival of the fittest means survival of the strongest It is referring to REPRODUCTIVE SUCCESS Misconception #2: Evolution involves some grand plan of nature in which species become progressively more perfect Organisms do not develop certain traits because they need them There is no such thing as “genetic perfection”

Evolution and Adaptation Co-Evolution Populations of two different species interacting over a long period of time Changes in the gene pool of one species can lead to changes the gene pool of another species Predator-prey relationships Plant defense mechanisms

Ecological Niches and Habitats Occupation Ecological niche Total way of life or functional role of a species in an ecosystem Habitat Physical location of a species Address

Ecological Niches and Adaptation Fundamental niche Full potential range of the physical, chemical, and biological factors a species can use if there were no direct competition from other species Realized niche Parts of a species’ fundamental niche that are actually used

Broad and Narrow Niches Generalist species Species with a broad ecological niche Live in many different places Eat a variety of food Tolerate a wide range of environmental conditions Ex: flies, mice, deer, catfish, humans Specialist species Species with a narrow ecological niche Live only in one type of habitat Use only a few types of food Tolerate only a narrow range of climatic and other environmental conditions Ex: tiger salamander, spotted owls, pandas

Generalist and Specialist Species: Broad and Narrow Niches Generalist species tolerate a wide range of conditions Specialist species can only tolerate a narrow range of conditions

Is it better to be a Generalist or a Specialist? Answer: It depends

Speciation, Extinction, and Biodiversity Speciation - formation of two species from one species because of divergent natural selection Geographic isolation – groups of the same species become physically separated

Geographic Isolation …can lead to reproductive isolation, divergence of gene pools and speciation.

Speciation, Extinction, and Biodiversity Reproductive Isolation – isolated populations become so genetically different they cannot . . . Interbreed Produce live, fertile offspring

Extinction: Lights Out Extinction occurs when the population cannot adapt to changing environmental conditions The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate

Extinction: Lights Out 99.9 % of all species that ever existed are now extinct

Species and families experiencing mass extinction Bar width represents relative number of living species Millions of years ago Era Period Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50–100 years. Quaternary Today Cenozoic Tertiary Extinction 65 Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Cretaceous Mesozoic Jurassic Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks. 180 Triassic Extinction Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. 250 Permian Carboniferous Extinction 345 Figure 4.12 Fossils and radioactive dating indicate that five major mass extinctions (indicated by arrows) have taken place over the past 500 million years. Mass extinctions leave many organism roles (niches) unoccupied and create new niches. Each mass extinction has been followed by periods of recovery (represented by the wedge shapes) called adaptive radiations. During these periods, which last 10 million years or longer, new species evolve to fill new or vacated niches. Many scientists say that we are now in the midst of a sixth mass extinction, caused primarily by human activities. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites. Devonian Paleozoic Silurian Ordovician Extinction 500 Ordovician: 50% of animal families, including many trilobites. Cambrian

Extinction Background extinction Mass extinction Normal extinction of various species as a result of changes in local environmental conditions Mass extinction Extinction resulting from catastrophic, wide-spread event in which large groups of existing species are wiped out

Period of Recovery Following Extinction Adaptive radiation - Process in which numerous new species evolve to fill vacant and new ecological niches in changed environments

How do speciation and extinction affect biodiversity? Speciation – Extinction = Biodiversity Extinctions and depletions temporarily reduce biodiversity YET create evolutionary opportunities for surviving species to undergo adaptive radiations to fill unoccupied and new biological niches

Effects of Humans on Biodiversity The scientific consensus is that human activities are decreasing the earth’s biodiversity