4 Ecology and evolution: Populations, communities, and biodiversity

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<ul><li> Slide 1 </li> <li> 4 Ecology and evolution: Populations, communities, and biodiversity </li> <li> Slide 2 </li> <li> This lecture will help you understand: How evolution generates biodiversity Speciation, extinction, and the biodiversity crisis Population ecology Community ecology Species interactions Conservation challenges Evolution by natural selection </li> <li> Slide 3 </li> <li> Key Words adaptation adaptive trait age distribution age structure age structure diagrams allopatric speciation anthropogenic artificial selection biodiversity biological diversity biosphere biotic potential carnivores carrying capacity climax community clumped distribution community competition decomposers density dependent detritivores ectoparasites Emigration endemic endoparasites environmental resistance evolution exponential growth extinction food chain food web fossil fossil record growth rate habitat selection habitats herbivores heritable host immigration interspecific competition intraspecific competition invasive species keystone species K-strategist limiting factors logistic growth mass extinction mutations mutualism natural selection niche omnivores parasite parasitism </li> <li> Slide 4 </li> <li> Key Words phylogenetic trees pioneer species pollination population density population dispersion population distribution population growth curves population size predation predator prey primary consumers primary succession random distribution resource partitioning r-strategists secondary consumers secondary succession sex ratio speciation species succession symbioses tertiary consumers trophic levels uniform distribution </li> <li> Slide 5 </li> <li> Central Case: Striking Gold in a Costa Rican Cloud Forest The golden toad of Monteverde, discovered in 1964, had disappeared 25 years later. Researchers determined that warming and drying of the forest was most likely responsible for its extinction. As the global climate changes, more such events can be expected. </li> <li> Slide 6 </li> <li> Biodiversity Biodiversity, or biological diversity, is the sum of an areas organisms, considering the diversity of species, their genes, their populations, and their communities. A species is a particular type of organism; a population or group of populations whose members share certain characteristics and can freely breed with one another and produce fertile offspring. </li> <li> Slide 7 </li> <li> Biodiversity Costa Ricas Monteverde cloud forest is home to many species and possesses great biodiversity. Figure 5.1 </li> <li> Slide 8 </li> <li> Natural selection Natural selection rests on three indisputable facts: Organisms produce more offspring than can survive. Individuals vary in their characteristics. Many characteristics are inherited by offspring from parents. </li> <li> Slide 9 </li> <li> Natural selection THEREFORE, logically Some individuals will be better suited to their environment; they will survive and reproduce more successfully. These individuals will transmit more genes to future generations. Future generations will thus contain more genes from better-suited individuals. Thus, characteristics will evolve over time to resemble those of the better-suited ancestors. </li> <li> Slide 10 </li> <li> Natural selection Fitness = the likelihood that an individual will reproduce and/or the number of offspring an individual produces over its lifetime Adaptive trait, or adaptation = a trait that increases an individuals fitness </li> <li> Slide 11 </li> <li> Natural selection Evidence of natural selection is all around us: In nature Diverse bills have evolved among species of Hawaiian honeycreepers. Figure 4.23a </li> <li> Slide 12 </li> <li> Beak Types Resulting From Natural Selection Unknown finch ancestor Insect and nectar eatersFruit and seed eaters Greater Koa-finch Kona Grosbeak Akiapolaau Maui Parrotbill Kuai Akialoa Amakihi Crested Honeycreeper Apapane </li> <li> Slide 13 </li> <li> Natural selection Evidence of natural selection is all around us: and in our domesticated organisms. Figure 4.23b Dog breeds, types of cattle, improved crop plantsall result from artificial selection (natural selection conducted by human breeders). </li> <li> Slide 14 </li> <li> Speciation The process by which new species come into being Speciation is an evolutionary process that has given Earth its current species richnessmore than 1.5 million described species and likely many million more not yet described by science. Allopatric speciation is considered the dominant mode of speciation, and sympatric speciation also occurs. </li> <li> Slide 15 </li> <li> Allopatric speciation 1.Single interbreeding population 2.Population divided by a barrier; subpopulations isolated Figure 5.2 </li> <li> Slide 16 </li> <li> Allopatric speciation 3.The two populations evolve independently, diverge in their traits. 4.Populations reunited when barrier removed, but are now different enough that they dont interbreed. Figure 5.2 </li> <li> Slide 17 </li> <li> Allopatric speciation Many geological and climatic events can serve as barriers separating populations and causing speciation. on. </li> <li> Slide 18 </li> <li> Formation of the earths early crust and atmosphere Small organic molecules form in the seas Large organic molecules (biopolymers) form in the seas First protocells form in the seas Single-cell prokaryotes form in the seas Single-cell eukaryotes form in the seas Variety of multicellular organisms form, first in the seas and later on land Chemical Evolution (1 billion years) Biological Evolution (3.7 billion years) </li> <li> Slide 19 </li> <li> Click to view animation. Stanley Miller's experiment animation. </li> <li> Slide 20 </li> <li> Stabilizing Selection Click to view animation. </li> <li> Slide 21 </li> <li> Disruptive Selection Click to view animation. </li> <li> Slide 22 </li> <li> Niches and Natural Selection Region of niche overlap Generalist species with a broad niche Specialist species with a narrow niche Niche breadth Niche separation Number of individuals Resource use </li> <li> Slide 23 </li> <li> Various Niches and Their Adaptations Black skimmer seizes small fish at water surface Flamingo feeds on minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation Brown pelican dives for fish, which it locates from the air Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Louisiana heron wades into water to seize small fish Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Knot (a sandpiper) picks up worms and small crustaceans left by receding tide Herring gull is a tireless scavenger Ruddy turnstone searches under shells and pebbles for small invertebrates Piping plover feeds on insects and tiny crustaceans on sandy beaches </li> <li> Slide 24 </li> <li> Geographic Separation Early fox population Spreads northward and southward and separates Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Gray Fox Arctic Fox Different environmental conditions lead to different selective pressures and evolution into two different species. Northern population Southern population </li> <li> Slide 25 </li> <li> Mimicry Span worm Bombardier beetle Viceroy butterfly mimics monarch butterfly Foul-tasting monarch butterfly Poison dart frog When touched, the snake caterpillar changes shape to look like the head of a snake Wandering leaf insect Hind wings of io moth resemble eyes of a much larger animal </li> <li> Slide 26 </li> <li> Phylogenetic trees Lifes diversification results from countless speciation events over vast spans of time. Evolutionary history of divergence is shown with diagrams called phylogenetic trees. Similar to family genealogies, these show relationships among organisms. </li> <li> Slide 27 </li> <li> Phylogenetic trees These trees are constructed by analyzing patterns of similarity among present-day organisms. This tree shows all of lifes major groups. Figure 5.4 </li> <li> Slide 28 </li> <li> Phylogenetic trees Within the group Animals in the previous slide, one can infer a tree of the major animal groups. Figure 5.4 </li> <li> Slide 29 </li> <li> Phylogenetic trees And within the group Vertebrates in the previous slide, one can infer relationships of the major vertebrate groups, and so on Figure 5.4 </li> <li> Slide 30 </li> <li> Extinction Extinction is the disappearance of an entire species from the face of the Earth. Average time for a species on Earth is ~110 million years. Species currently on Earth = the number formed by speciation minus the number removed by extinction. </li> <li> Slide 31 </li> <li> Extinction Some species are more vulnerable to extinction than others: Species in small populations Species adapted to a narrowly specialized resource or way of life Monteverdes golden toad was apparently such a specialist, and lived in small numbers in a small area. </li> <li> Slide 32 </li> <li> Extinction Some species are more vulnerable to extinction than others: Species in small populations Species adapted to a narrowly specialized resource or way of life Monteverdes golden toad was apparently such a specialist, and lived in small numbers in a small area. </li> <li> Slide 33 </li> <li> Lifes hierarchy of levels Life occurs in levels: from the atom up to the molecule to the cell to the tissues to the organs to the organism Figure 5.7 </li> <li> Slide 34 </li> <li> Lifes hierarchy of levels and from the organism to the population to the community to the ecosystem to the biosphere. Ecology deals with these levels, from the organism up to the biosphere. Figure 5.7 </li> <li> Slide 35 </li> <li> Ecology The study of: the distribution and abundance of organisms, the interactions among them, and the interactions between organisms and their abiotic environments Ecology is NOT environmental advocacy! (= a common MISUSE of the term) </li> <li> Slide 36 </li> <li> Habitat and niche Habitat = the specific environment where an organism lives (including living and nonliving elements: rocks, soil, plants, etc.) Habitat selection = the process by which organisms choose habitats among the options encountered Niche = an organisms functional role in a community (feeding, flow of energy and matter, interactions with other organisms, etc.) </li> <li> Slide 37 </li> <li> Population ecology Population = a group of individuals of a species that live in a particular area Several attributes help predict population dynamics (changes in population): Population size Population density Population distribution Age structure Sex ratio </li> <li> Slide 38 </li> <li> Population size Number of individuals present at a given time Population size for the golden toad was 1,500+ in 1987, and zero a few years later. </li> <li> Slide 39 </li> <li> Population density Number of individuals per unit area or, Number of individuals per unit volume Population density for the harlequin frog increased locally as streams dried and frogs clustered in splash zones. </li> <li> Slide 40 </li> <li> Population distribution Spatial arrangement of individuals Figure 5.8 Random Clumped Uniform </li> <li> Slide 41 </li> <li> Age structure Or age distribution = relative numbers of individuals of each age or age class in a population Age structure diagrams, or age pyramids, show this information. Figure 5.9 </li> <li> Slide 42 </li> <li> Age structure Figure 5.9 Pyramid weighted toward young: population growing Pyramid weighted toward old: population declining </li> <li> Slide 43 </li> <li> Sex ratio Ratio of males to females in a population Even ratios (near 50/50) are most common. Fewer females causes slower population growth. Note human sex ratio biased toward females at oldest ages. </li> <li> Slide 44 </li> <li> Population growth Populations grow, shrink, or remain stable, depending on rates of birth, death, immigration, and emigration. (birth rate + immigration rate) (death rate + emigration rate) = population growth rate </li> <li> Slide 45 </li> <li> Exponential growth Unregulated populations increase by exponential growth: Growth by a fixed percentage, rather than a fixed amount. Similar to growth of money in a savings account </li> <li> Slide 46 </li> <li> Exponential growth in a growth curve Population growth curves show change in population size over time. Scots pine shows exponential growth Figure 5.10 </li> <li> Slide 47 </li> <li> Limits on growth Limiting factors restrain exponential population growth, slowing the growth rate down. Population growth levels off at a carrying capacitythe maximum population size of a given species an environment can sustain. Initial exponential growth, slowing, and stabilizing at carrying capacity is shown by a logistic growth curve. </li> <li> Slide 48 </li> <li> Logistic growth curve Figure 5.11 </li> <li> Slide 49 </li> <li> Population growth: Logistic growth Logistic growth (shown here in yeast from the lab) is only one type of growth curve, however. Figure 5.12a </li> <li> Slide 50 </li> <li> Population growth: Oscillations Some populations fluctuate continually above and below carrying capacity, as with this mite. Figure 5.12b </li> <li> Slide 51 </li> <li> Population growth: Dampening oscillations In some populations, oscillations dampen, as population size settles toward carrying capacity, as with this beetle. Figure 5.12c </li> <li> Slide 52 </li> <li> Population growth: Crashes Some populations that rise too fast and deplete resources may then crash, as with reindeer on St. Paul Island. Figure 5.12d </li> <li> Slide 53 </li> <li> Density dependence Often, survival or reproduction lessens as populations become more dense. Density-dependent factors (disease, predation, etc.) account for the logistic growth curve. </li> <li> Slide 54 </li> <li> Biotic potential and reproductive strategies Species differ in strategies for producing young. Species producing lots of young (insects, fish, frogs, plants) have high biotic potential. Others, such as mammals and birds, produce few young. However, those with few young give them more care, resulting in better survival. </li> <li> Slide 55 </li> <li> Biotic Potential POPULATION SIZE Growth factors (biotic potential) Favorable light Favorable temperature Favorable chemical environment (optimal level of critical nutrients) Abiotic Biotic High reproductive rate Generalized niche Adequate food supply Suitable habitat Ability to compete for resources Ability to hide from or defend against predators Ability to resist diseases and parasites Ability to migrate and live in other habitats Ability to adapt to environmental change Decrease factors (environmental resistance) Too much or too little light Temperature too high or too low Unfavorable chemical environment (too much...</li></ul>