Ecology Midterm Study Guide PDF

ECOLOGY MIDTERM STUDY GUIDE INTRODUCTION TO ECOLOGY Ecology- The scientific study of interactions among organisms and between organisms and the environment. Biosphere - combined portions of the planet in which all of life exists, including land, water, and atmosphere LEVELS OF ORGANIZATION OF AN E...

ECOLOGY MIDTERM STUDY GUIDE INTRODUCTION TO ECOLOGY Ecology- The scientific study of interactions among organisms and between organisms and the environment. Biosphere - combined portions of the planet in which all of life exists, including land, water, and atmosphere LEVELS OF ORGANIZATION OF AN ECOSYSTEM species/individual → population → community → ecosystem → biome → biosphere SPECIES Group of organisms so similar to one another that they can breed and produce fertile offspring. POPULATION Same species and live in the same area. COMMUNITY Different populations live together in a defined area. ECOSYSTEM A collection of all organisms that live in a particular place together with their nonliving environment. BIOME A group of ecosystems that have the same climate and similar dominant communities. BIOSPHERE FACTORS THAT AFFECT AN ECOSYSTEM Biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which an organism lives. BIOTIC FACTORS  -​ Living factors that influence ecosystem -​ Plant life -​ Animal life ABIOTIC FACTOR -​ Physical, non-living factors that influence an ecosystem -​ Examples: temperature, precipitation, humidity, wind, nutrients, sunlight OTHER FACTORS THAT AFFECT AN ECOSYSTEM -​ The area where an organism lives is called its habitat -​ Habitats provide populations of wildlife with food, water, shelter and space -​ A niche is the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions. It is an organisms’ occupation SYMBIOTIC RELATIONSHIPS There are three different types of symbiotic relationships 1.​ Mutualism is when two or more organisms live closely together and they each benefit from each other in the relationship 2.​ Commensalism is when two or more organisms live closely together and one organism benefits from the other, but the other organism is neither helped nor harmed 3.​ Parasitism is when one organism benefits at the expense of another organism +​ Parasites can be either endoparasitic, like roundworms, tapeworms, flukes, and bacteria, or they can be ectoparasitic like fleas and ticks +​ Another type of parasitism is called brood parasitism. An example of this is the brown-headed cowbird which lays its egg in another bird’s nest. The bird then hatch and often push the other birds out of the nest MUTUALISM One of the best examples of mutualism is insect pollination in plants. The plant benefits by cross-pollination of its flowers. The insect benefits by obtaining food from pollen. COMMENSALISM A remoras fish attached to a shark would be an example of commensalism. The remoras receive a free ride and free meal from the scraps that the shark does not eat. The remoras neither help nor harm the shark. PARASITISM Head lice, mosquitos, and dog heartworms are all examples of parasitism. CYCLES THAT AFFECT ECOSYSTEMS WATER CYCLE The water cycle describes how water evaporates from the surface of the earth, rises into the atmosphere, cools and condenses into rain and snow in clouds, and falls again to the surface as precipitation. WATER CYCLE DEFINITIONS -​ Evaporation: process of becoming a vapor; liquid to a gas -​ Condensation: state of matter from gas to liquid; reverse of vaporization -​ Precipitation: the amount of water that falls to earth as snow, sleet, hail, rain, mist -​ Transpiration: loss of water from a plant through its leaves -​ Runoff: the flow of water, from snow and rain -​ Infiltration: the process by which water on the ground enters the soil CARBON CYCLE -​ CO2 is taken in by photosynthetic organisms -​ Carbon is eventually released during respiration -​ Carbon gets locked up in coal, oil, calcium carbonate (shells) -​ Excess CO2 in the atmosphere causes problems -​ The parts of the cycle that remove carbon dioxide from the atmosphere (vegetation) care called carbon sinks -​ The parts of the cycle that release carbon dioxide are called carbon sources -​ Burning of fuels generates huge quantities of carbon dioxide that cannot be taken up fast enough by the carbon sinks. This excess carbon dioxide contributes to global warming CO2 CYCLE DESCRIPTION -​ Plants release O2 into atmosphere as a waste product -​ Animals release CO2 into atmosphere as a waste product -​ Factories and cars release CO2 into the atmosphere through combustion -​ Plants use CO2 during photosynthesis and animals use O2 for respiration ENERGY FLOW -​ Every organism needs energy to power life’s process -​ The flow of energy through an ecosystem is the most important factors that determines the ability to sustain life NITROGEN CYCLE The nitrogen cycle involves specialized bacteria, Nitrogen cycle = describes the routes that nitrogen atoms take through the environment -​ Nitrogen gas cannot be used by most organisms -​ Nitrogen fixation = lightning or nitrogen-fixing bacteria combine (fix) nitrogen with hydrogen to form ammonium, which can be used by plants, Animals obtain nitrogen by eating plants or other animals -​ Decomposers get nitrogen from dead and decaying plants or other animals, releasing ammonium ions to nitrifying bacteria, Denitrifying bacteria = bacteria that convert nitrates in soil or water to gaseous nitrogen, releasing it back into the atmosphere and completing the nitrogen cycle NITROGEN CYCLE -​ Nitrogen is needed for the formation of amino acids, peptides, nucleic acids (build proteins). Decomposers release nitrogen from head organisms (or from waste and parts of organisms) -​ Nitrogen fixing bacteria - “fix” nitrogen or make it into a more useful form NH3 (ammonia) -​ Excess nitrogen causes loss of soil nutrients, acidification of rivers and lakes, encourages the spread of weeds, algal blooms WE HAVE GREATLY INFLUENCED THE NITROGEN CYCLE -​ Overuse of fertilizers has negative side effects: +​ Increases the flux of nitrogen from the atmosphere to the land  +​ Causes eutrophication in estuaries and coastal ecosystems and fisheries +​ Washes essential nutrients out of the soil -​ Burning fossil fuels adds nitrogen compounds to the atmosphere that contributes to acid precipitation PHOSPHORUS CYCLE describes the routes that phosphorus atoms take through the environment. -​ Phosphorus (P) is a key component of cell membranes, DNA, RNA, ATP, and ADP. -​ Most phosphorus is within rocks -​ It is released by weathering PHOSPHORUS CYCLE -​ Phosphorus is an important mineral released from rocks -​ The availability of phosphorus in the environment has a huge effect on productivity -​ Excess can cause problems: algal blooms, population, explosions WE AFFECT THE PHOSPHORUS CYCLE -​ Humans add phosphorus to fertilizers to promote crop growth -​ Runoff from farm fields and lawns contains phosphorus +​ Increases phytoplankton growth +​ Results in eutrophication and hypoxia -​ Wastewater discharge also releases phosphorus +​ Detergents have traditionally contained high levels of phosphates ECOLOGICAL SUCCESSION the process by which the mix of species and habitat in an area changes over time. ECOLOGICAL SUCCESSION -​ A series of predictable changes in an environment. -​ The process by which the mix of species and habitat in an area changes over time SUCCESSION -​ Primary succession: succession that occurs on the surface where no soil exists -​ Pioneer species first species to populate that area  -​ Examples: lichen and moss EXAMPLE OF PIONEER SPECIES Lichen PRIMARY SUCCESSION (no life already existed here) SUCCESSION -​ Secondary succession: following a disturbance that destroys a community without destroying soil -​ Example: land cleared and plowed for farming -​ Example: fires set by lightning PHYSICAL ENVIRONMENT BIOTIC FACTORS -​ Living factors that influence ecosystem -​ Plant life -​ Animal life ABIOTIC FACTOR -​ Physical, non-living factors that influence an ecosystem -​ Examples: temperature, precipitation, humidity, wind, nutrients, sunlight CLIMATE Four major abiotic components of climate are temperature, water, sunlight, and wind Microclimate vs macroclimate TEMPERATURE -​ Environment temperature is an important factor in distribution of organisms because of its effects on biological processes -​ Cells may freeze and rupture below 0℃, while most proteins denature above 45℃ -​ Mammals and birds expend energy to regulate their internal temperature RANGE OF TOLERANCE -​ Temperature -​ pH -​ Water Balance WATER -​ Water availability in habitats is another important factor in species distribution -​ Desert organisms exhibit adaptations for water conservation SALINITY -​ Salt concentration affects water balance of organisms through osmosis -​ Few terrestrial organisms are adapted to high-salinity habitats SUNLIGHT The sun is the source of all energy for earth. -​ Light intensity and quality affect photosynthesis -​ Water absorbs light, thus in aquatic environments most photosynthesis occurs near the surface -​ In deserts, high light levels increase temperature and can stress plants and animals ROCKS AND SOIL Many characteristics of soil limit distribution of plants and thus the animals that feed upon them: -​ Physical structure -​ pH -​ Mineral composition CLIMATE  -​ Four major abiotic components of climate are temperature, water, sunlight, and wind -​ The long-term prevailing weather conditions in an area constitute its climate -​ Macroclimate consists of patterns on the global, regional, and local level -​ Microclimate consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen log GLOBAL CLIMATE PATTERNS -​ Global climate patterns are determined largely by solar energy and the planet’s movement in space -​ Sunlight intensity plays a major party in determining the Earth’s climate patterns -​ More heat and light per unit surface area teach the tropics than high latitudes PRECIPITATION PATTERNS ARE INFLUENCED BY LATITUDE AND SURFACE TEMPERATURE 2 major cells of circulating air result in a pattern of high precipitation near the equator, and lower precipitation nearing the poles. -​ Hadley cell - large-scale atmospheric circulation where air rises near the equator, flow poleward, and descends in the subtropics (30 degrees latitude) -​ Ferrel cell - zone of mixing, secondary cell, mid-latitude segment of the earth’s windflow (30-60 degrees) -​ Polar cell: least solar radiation, little or no precipitation CLIMATE PATTERNS -​ Global air circulation and precipitation patterns play major roles in determining climate patterns -​ Warm wet air flows from the tropics toward the poles -​ Air flowing close to Earth’s surface creates predictable global wind patterns -​ Cooling trade winds blow from east to west in the tropics; prevailing westerlies blow from west to east in the temperate zones REGIONAL, LOCAL, AND SEASONAL EFFECTS ON CLIMATE -​ Proximity to bodies of water and topographic features contribute to local variations in climate -​ Seasonal variation also influences climate -​ The Gulf Stream carries warm water from the equator to the North Atlantic  -​ Oceans and their currents and large lakes moderate the climate of nearby terrestrial environments -​ During the day, air rises over warm land and draws a cool breeze from the water across the land -​ As the land cools at night, air rises over the warmer water and draws cooler air from land back over the water, which is replaced by warm air from offshore MOUNTAINS -​ Mountains have a significant effect on: +​ The amount of sunlight reaching an area +​ Local temperature +​ Rainfall -​ Rising air releases moisture on the windward side of a peak and creates a “rain shadow” as it absorbs moisture on the leeward side SEASONALITY -​ The angle of the sun leads to many seasonal changes in local environments -​ Lakes are sensitive to seasonal temperature change and experience seasonal turnover MICROCLIMATE Microclimate is determined by fine-scale differences in the environment that affect light and wind patterns. LONG-TERM CLIMATE CHANGE -​ Global climate change will profoundly affect the biosphere -​ One way to predict future global climate change is to study previous changes  -​ As glaciers began retreating 16,000 years ago, tree distribution patterns changed -​ As climate changes, species that have difficulty dispersing may have smaller ranges or could become extinct MICROEVOLUTION VS. MACROEVOLUTION -​ Microevolution: survival through the inheritance of favorable characteristics +​ Mutations +​ Selection -​ Macroevolution: progression of biodiversity through geologic time +​ Speciation +​ Extinction BIOMES Biomes are the major ecological associations that occupy broad geographic regions of land or water -​ Varying combinations of biotic and abiotic factors determine the nature of biomes AQUATIC BIOMES AQUATIC BIOMES ARE DIVERSE AND DYNAMIC SYSTEMS THAT COVER MOST OF EARTH -​ Biomes are the major ecological associations that occupy broad geographic regions of land or water -​ Varying combinations of biotic and abiotic factors determine the nature of biomes -​ Aquatic biome account for the largest part of the biosphere in terms of area -​ They can contain freshwater or saltwater (marine) -​ Oceans cover 75% of Earth’s surface and have an enormous impact on the biosphere STRATIFICATION OF AQUATIC BIOMES -​ Many aquatic biomes are stratified into zones or layers defined by light penetration, temperature, and depth -​ The upper photic zones has sufficient light for photosynthesis while the lower aphotic zone receives little light -​ The organic and inorganic sediment as the bottom of all aquatic zones is called the benthic zone -​ The communities of organisms in the benthic zone are collectively called the benthos  -​ Detritus, dead organic matter, falls from the productive surface water and is an important source of food -​ The most extensive part of the ocean is the abyssal zone with a depth of 2,000 to 6,000 m -​ In oceans and most lakes, a temperature boundary called the thermocline separates the warm upper layer from the cold deeper water -​ Many lakes undergo a semiannual mixing of their waters called turnover -​ Turnover mixes oxygenated water from the surface with nutrient-rich water from the bottom AQUATIC BIOMES -​ Major aquatic biomes can be characterized by their physical environment, chemical environment, geological features, photosynthetic organisms, and heterotrophs. -​ Rooted and floating aquatic plants live in the shallow and well-lighted littoral zone -​ Water is too deep in the limnetic zone to support rooted aquatic plants, small drifting animals called zooplankton graze on the phytoplankton LAKES -​ Oligotrophic lakes are nutrient-poor and generally oxygen-rich -​ Eutrophic lakes are nutrient-rich and often depleted of oxygen if ice covered in winter WETLANDS -​ A wetland is a habitat that is inundated by water at least some of the time and that supports plants adapted to water-saturated soil -​ Wetlands can develop in shallow basins, along flooded river banks, or on the coasts of large lakes and seas -​ Wetlands are among the most productive biomes one earth and are home to diverse invertebrates and birds STREAMS AND RIVERS -​ The most prominent physical characteristics of streams and rivers is current -​ A diversity of fishes and invertebrates inhabit unpolluted rivers and streams -​ Damming and flood control impair natural functioning of stream and river ecosystems ESTUARIES -​ An estuary is a transition area between river and sea -​ Salinity varies with the rise and fall of the tides -​ Estuaries are nutrient rich and highly productive -​ An abundant supply of food attracts marine invertebrates and fish INTERTIDAL ZONES -​ An intertidal zones is periodically submerged and exposed by the tides -​ Intertidal organisms are challenged by variations in temperature and salinity and by the mechanical forces of wave action -​ Many animals of rocky intertidal environments have structural adaptations that enable them to attack to the hard substance OCEANIC PELAGIC ZONES -​ The oceanic pelagic biome is a vast realm of open blue water, constantly mixed by wind-driven oceanic currents -​ This biome covers approximately 70% of Earth’s surface -​ Phytoplankton and zooplankton are the dominant organisms in this biome; also found are free-swimming animals CORAL REEFS -​ Coral reefs are formed from the calcium carbonate skeletons of coral -​ Corals require a solid substrate for attachment -​ Unicellular algae live within the tissues of the corals and form a mutualistic relationship that provides the corals with organics molecules MARINE BENTHIC ZONE -​ The marine benthic zone consists of the seafloor below the surface waters of the coastal, or neritic, zone and the offshore pelagic zone -​ Organisms is the very deep benthic, or abyssal, zone are adapted to continuous cold and extremely high water pressure -​ Unique assemblages of organisms are associated with deep-sea hydrothermal vents of volcanic origin on mid-oceanic ridges, here the autotrophs are chemoautotrophic prokaryotes  -​ Unique assemblages of organisms are associated with deep-sea hydrothermal vents of volcanic origin on mid-oceanic ridges; here the autotrophs are chemoautotrophic prokaryotes TERRESTRIAL BIOMES The structure and distribution of terrestrial biomes are controlled by slimate and disturbance. -​ Vertical layering TERRESTRIAL BIOMES Terrestrial biomes can be characterized by distribution, precipitation, temperature, plants, and animals. TROPICAL FOREST - CAN BE RAIN OR DRY FORESTS -​ In tropical rainforests, rainfall is relatively constant, while in tropical dry forests precipitation is highly seasonal -​ Tropical forests are vertically layered and competition for light is intense -​ Tropical forests are home to millions of animals species DESERTS -​ Precipitation is low and highly variable, deserts may be hot or cold -​ Desert plants are adapted for heat and dedication tolerance, water storage, and reduced leaf surface area -​ Common desert animals include many kinds of snakes, lizards, scorpions, ants, beetles, migratory and resident birds, and seed-eating rodents, many are nocturnal SAVANNAH -​ Savanna precipitation and temperature are seasonal -​ Grasses and forbs make up most if the ground cover -​ Common inhabitants include insects, and mammals such as wildebeests, zebras, lions, and hyenas CHAPARRAL -​ Chaparral climate is highly seasonal, with cool and rainy winters and hot dry summers -​ The chaparral is dominated by shrubs, small trees, grasses, and herbs; many plants are adapted to fire and drought  -​ Animals include amphibians, birds and other reptiles, insects, small mammals and browsing mammals TEMPERATE GRASSLAND -​ Temperate grasslands are found on many continents -​ Winters are cold and dry, while summers are wet and hot -​ The dominant plants, grasses and forbs, are adapted to droughts and fires -​ Native mammals include large grazers and small burrowers NORTHERN CONIFEROUS FOREST -​ The northern coniferous forest, or taiga, extends across northern North America and Eurasia and is the largest terrestrial biome on earth -​ Winters are cold and long while summers may be hot -​ The conical shape of conifers prevent too much snow from accumulating and breaking their branches -​ Animals include migratory and resident birds, and large mammals TEMPERATE BROADLEAF FOREST -​ Winters are cool, while summers are hot and humid; significant precipitation falls year round as rain and snow -​ A mature temperate broadleaf forest has vertical layers dominated by deciduous trees in the Northern Hemisphere and evergreen eucalyptus Australia -​ Mammals, birds, and insects make use of all vertical layers in the forest -​ In the Northern Hemisphere, many mammals hibernate in the winter TUNDRA -​ Tundra covers expansive areas of the Arctic; alpine tundra exists on high mountaintops at all latitudes -​ Winter are long and cold while summers are relatively cool; precipitation varies -​ Permafrost, a permanently frozen layer of soil, prevents water infiltration -​ Vegetation is herbaceous (mosses, grasses, forbes, dwarf shrubs and trees, and lichen) and support birds, grazers, and their predators GENETICS AND NATURAL SELECTION Darwin noted that current species are descendants of ancestral species -​ Evolution can be defined by Darwin’s phrase descent with modification: The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past Natural selection does not create new traits, but edits or selects for traits already present in the population Homology is similarity resulting from common ancestry Vestigial structures are remnants of features that served important functions in the organism’s ancestors Evolutionary trees are hypotheses about the relationships among different groups Convergent evolution is the evolution of similar, or analogous, features in distantly related groups. Convergent evolution does not provide information about ancestry EVOLUTION IS HOW AN ENTITY CHANGES THROUGH TIME Natural populations exhibit variation -​ Species accumulate difference over time -​ Descendants differ from their ancestors -​ New species arise from existing ones Development of modern concept of evolution traced to Darwin -​ “Descent with modification” DARWIN -​ Darwin noted that current species are descendants of ancestral species -​ Evolution can be defined by Darwin’s phrase descent with modification -​ Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life +​ Some doubt about the permanence of species preceded Darwin’s ideas DARWIN’S FOCUS ON ADAPTATIONS  -​ Darwin perceived adaptations to the environment and the origin of new species are closely related processes -​ From studies made years after Darwin’s voyage, biologists have concluded that this is what happened to the Galapagos finches -​ In 1844, Darwin wrote an essay on natural selection as the mechanism of descent with modification, but did not introduce his theory -​ Natural selection is a process in which individuals with favorable inherited traits are more likely to survive and reproduce +​ Individuals that already have a favorable trait that allows survival will now become more popular, NOT individuals changing to match the environment DARWIN'S THEORY -​ Note that individuals do not evolve; populations evolve over time -​ Natural selection can only increase or decrease heritable traits that vary in a population -​ Adaptations vary with different environments -​ Natural selection does not create new traits, but edits or selects for traits already present in the population -​ The local environment determines which traits will be selected for or selected against in any specific population SPECIATION The formation of new and distinct species in the course of evolution. -​ Does not change because of the environment, it changes as species survive and reproduce. -​ The variety comes in the survival of populations and genes that are able to survive ARTIFICIAL SELECTION, NATURAL SELECTION, AND ADAPTATION -​ Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection  -​ Darwin drew two inferences from two observations +​ Observation #1: Members of a population often vary in their inherited traits +​ Observation #2: All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce +​ Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals +​ Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations ​ If some heritable traits are advantageous, these will accumulate in a population over time, and this will increase the frequency of individuals with these traits ​ This process explains the match between organisms and their environment NATURAL SELECTION -​ Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals -​ Natural selection increases the adaptation of organisms to their environment over time -​ If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species NATURAL SELECTION CAN CHANGE THE DISTRIBUTION OF A TRAIT IN ONE OF THREE WAYS -​ Macroevolution is evolution within a population. +​ observable change in the allele frequencies +​ can result from natural selection -​ Natural selection can take one of three paths 1.​ Directional selection favors phenotypes at one extreme 2.​ Stabilizing selection favors that intermediate phenotype 3.​ Disruptive selection favors both extreme phenotypes HOMOLOGY Similarly resulting from common ancestry. ANATOMICAL AND MOLECULAR HOMOLOGIES -​ Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor -​ Comparative embryology reveals anatomical homologies not visible in adult organisms -​ Vestigial structures are remnants of features that served important functions in the organism’s ancestors -​ Examples of homologies at the molecular level are genes shared among organisms inherited from common ancestors HOMOLOGIES AND “TREE THINKING” -​ Evolutionary trees are hypotheses about the relationships among different groups -​ Homologies form netted patterns in evolutionary trees -​ Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data A DIFFERENT CAUSE OF RESEMBLANCE: CONVERGENT EVOLUTION -​ Convergent evolution is the evolution of similar, or analogous, features in distantly related groups -​ Analogous traits arise when groups independently adapt to similar environments in similar ways -​ Convergent evolution does not provide information about ancestry GENETIC VARIATION Genetic variation in a population increases the chance that some individuals will survive. Genetic variation comes from several sources: Mutation, recombination during meiosis, hybridization KEY CONCEPT Populations, not individuals, evolve. NATURAL SELECTION ACTS ON DISTRIBUTION OF TRAITS NATURAL SELECTION CAN CHANGE THE DISTRIBUTION OF A TRAIT IN ONE OF THREE WAYS -​ Macroevolution is evolution within a population. +​ observable change in the allele frequencies +​ can result from natural selection -​ Natural selection can take one of three paths 1.​ Directional selection favors phenotypes at one extreme 2.​ Stabilizing selection favors that intermediate phenotype 3.​ Disruptive selection favors both extreme phenotypes KEY CONCEPT Natural selection is not the only mechanism through which populations evolve. -​ Genetic variation leads to phenotypic variation. -​ Phenotypic variation is necessary for natural selection. -​ Gene flow is the movement of alleles between populations. -​ Genetic drift is a change in allele frequencies due to chance. GENETIC DRIFT IS A CHANGE IN ALLELE FREQUENCIES DUE TO CHANCE -​ Genetic drift causes a loss of genetic diversity. -​ It is most common in small populations. -​ A population bottleneck can lead to genetic drift. +​ It occurs when an event drastically reduces population size. +​ The bottleneck effect is genetic drift that occurs after a bottleneck event. -​ The founding of a small population can lead to genetic drift. +​ It occurs when a few individuals start a new population. +​ The founder effect is genetic drift that occurs after the start of a new population. -​ Genetic drift has negative effects on a population. +​ less likely to have some individuals that can adapt +​ harmful alleles can become more common due to chance SEXUAL SELECTION OCCURS WHEN CERTAIN TRAITS INCREASEMATING SUCCESS -​ Natural selection arises through preference by one sex for certain characteristics in individuals of the other sex. -​ Sexual selection occurs due to the higher cost of reproduction for females. +​ males produce many sperm continuously +​ females are more limited in potential offspring each cycle -​ There are two types of sexual selection: 1.​ intrasexual selection: competition between members of the same sex (usually males) for access to mates 2.​ intersexual selection: males display certain traits to females members of one sex (usually females) choose members of the opposite sex. KEY CONCEPT New species can arise when populations are isolated. Speciation is the rise of two or more species from one existing species. THE ISOLATION OF POPULATIONS CAN LEAD TO SPECIATION -​ Populations become isolated when there is no gene flow. +​ Isolated populations adapt to their own environments. +​ Genetic differences can add up over generations. -​ Reproductive isolation can occur between isolated populations. +​ members of different populations cannot mate successfully +​ final step to becoming separate species -​ Speciation is the rise of two or more species from one existing species. POPULATIONS CAN BECOME ISOLATED IN SEVERAL WAYS -​ Behavioral barriers can cause isolation. +​ called behavioral isolation +​ includes differences in courtship or mating behaviors -​ Geographic barriers can cause isolation. +​ called geographic isolation +​ physical barriers divide the population -​ Temporal barriers can cause isolation. +​ called temporal isolation +​ timing of reproductive periods prevents mating EVOLUTION THROUGH NATURAL SELECTION IS NOT RANDOM -​ Natural selection can have direction. -​ The effects of natural selection add up over time. -​ Convergent evolution describes evolution toward similar traits in unrelated species. -​ Divergent evolution describes evolution toward different traits in closely related species. DIVERGENT VS CONVERGENT EVOLUTION SPECIES CAN SHAPE EACH OTHER OVER TIME -​ Two or more species can evolve together through coevolution +​ Evolutionary paths become connected +​ Species evolve in response to changes in each other -​ Coevolution can occur in beneficial relationships -​ Coevolution can occur in competitive relationships, sometimes called evolutionary -​ Coevolution is the process of reciprocal evolutionary change that occurs between pairs of species or among groups of species as they interact with one another SPECIES CAN BECOME EXTINCT -​ Extinction is the elimination of a species from Earth Due to loss and degradation of habitat (mainly deforestation), over exploitation (hunting, overfishing), invasive species, climate change, and nitrogen pollution. -​ Background extinctions occur continuously at a very low rate. +​ occur at roughly the same rate as speciation +​ usually affects a few species in a small area +​ caused by local changes in environment -​ Mass extinctions are rare but much more intense. +​ destroy many species at global level +​ thought to be caused by catastrophic events +​ at least five mass extinctions in last 600 m KEY CONCEPTS Speciation often occurs in patterns. SPECIATION OFTEN OCCURS IN PATTERNS -​ A pattern of punctuated equilibrium exists in the fossil record  +​ theory proposed by Eldredge and Gould in 1972 +​ episodes of speciation occur suddenly in geologic time +​ followed by long periods of little evolutionary change +​ revised Darwin’s idea that species arose through gradual transformations -​ Evolution by natural selection involves both change and “sorting” +​ New genetic variations arise by chance +​ Beneficial alleles are “sorted” and favored by natural selection -​ Only natural selection consistently results in adaptive evolution -​ Many species evolve from one species during adaptive radiation. +​ ancestral species diversifies into many descendent species +​ descendent species usually adapted to wide range of environments ADAPTIVE RADIATION Adaptive radiation - evolution of an animal or plant group into a wide variety of types adapted to specialized modes of life. -​ Adaptive radiations are best exemplified in closely related groups that have evolved in a relatively short time. THE KEY ROLE OF NATURAL SELECTION IN ADAPTIVE EVOLUTION Striking adaptation have arisen by natural selection -​ For example, cuttlefish can change color rapidly for camouflage -​ For example, the jaws of snakes allow them to swallow prey larger than their heads SPECIATION -​ Speciation, the origin of new species, is at the focal point of evolutionary theory. -​ Evolutionary theory must explain how new species originate and how populations evolve -​ Microevolution consists of changes in allele frequency in a population over time -​ Macroevolution refers to broad patterns of evolutionary change above the species PHYLOGENETIC SPECIES CONCEPT (PSC) -​ Focuses on shared derived characters (what do they shared among themselves)  -​ Species should be applied to groups of populations that have been evolving independently of other groups (phylogenetics take into account the evolutionary track between two different species) -​ Determined by molecular data, such as DNA groups -​ Can be applied to both loving and extinct organisms and provides insight into the evolutionary history of species CONCEPT: THE BIOLOGICAL SPECIES CONCEPT EMPHASIZES REPRODUCTIVE ISOLATION -​ Species is a Latin word meaning “kind” or “appearance” -​ Biologists compare morphology, physiology, biochemistry, and DNA sequences when grouping organisms THE BIOLOGICAL SPECIES CONCEPT emphasizes reproductive isolation, the biological species concept states that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations -​ Defines species as groups of interbreeding population that are reproductively isolated +​ Based on reproduction and offspring that survive +​ Reproductive isolation: cannot have reproduction that survive -​ Cannot be applied to fossils because their reproductive isolation cannot be evaluated. Additionally, it does not apply to asexual organisms or self-fertilizing organisms -​ Prezygotic barriers block fertilization from occurring: Habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation -​ Postzygotic barriers prevent the hybrid zygote from developing into a viable, fertile adult: Reduced hybrid viability, reduced hybrid fertility, hybrid breakdown PREZYGOTIC BARRIERS block fertilization from occurring by: -​ Impeding different species from attempting to mate -​ Preventing the successful completion of mating -​ Hindering fertilization if mating is successful PREZYGOTIC BARRIER: HABITAT ISOLATION Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers. PREZYGOTIC BARRIER: TEMPORAL ISOLATION Species that breed at different times of the day, different seasons, or different years cannot mix their gametes. PREZYGOTIC BARRIER: MECHANICAL ISOLATION Morphological differences can prevent successful mating. PREZYGOTIC BARRIER: GAMETIC ISOLATION Sperm of one species may not be able to fertilize eggs of another species. POSTZYGOTIC BARRIERS prevent the hybrid zygote from developing into a viable, fertile adult. -​ Reduced hybrid viability -​ Reduced hybrid fertility -​ Hybrid breakdown POSTZYGOTIC BARRIER: REDUCED HYBRID VIABILITY Genes of the different parent species may interact and impair the hybrid’s development. POSTZYGOTIC BARRIER: REDUCED HYBRID FERTILITY Even if hybrids are vigorous, they may be sterile. POSTZYGOTIC BARRIER: HYBRID BREAKDOWN Some first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile. MORPHOLOGICAL SPECIES CONCEPT concept defines a species by structural features. -​ Defines species based on physical characteristics, such as size, shape, and color +​ This does not provide that most information -​ Assumes that individuals belonging to the same species share similar morphological traits and that individuals belonging to different species have different traits  -​ Can be applied to both living and fossil organisms, making it a useful tool for studying evolutionary history -​ Does not require reproductive isolation to define species, it may not accurately reflect genetic differences between populations and may lump together populations that are reproductively isolated but have similar morphological traits ECOLOGICAL SPECIES CONCEPT views a species in terms of its ecological niche The phylogenetic species concept defines a species as the smallest group of individuals on a phylogenetic tree. -​ Defines species based on their ecological roles in a particular environment +​ How is energy consumed and transformed +​ Predators/prey +​ Who are they competing with -​ Assumes that individuals belonging to the same species occupy similar ecological niches and interact with their environment in similar ways -​ Can be applied to both living and extinct organisms and provides insight into the role of species in their ecosystem CONCEPT: SPECIATION CAN TAKE PLACE WITH OR WITHOUT GEOGRAPHIC SEPARATION Speciation can occur in two ways: Allopatric Speciation: A population forms a Sympatric Speciation: A subset of a new species while geographically isolated population forms a new species without from its parent population. geographic separation. ALLOPATRIC (“OTHER COUNTRY”) SPECIATION In allopatric speciation, gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations.  -​ For example, the flightless cormorant of the Galápagos likely originated from a flying species on the mainland THE PROCESS OF ALLOPATRIC SPECIATION The definition of barrier depends on the ability of a population to disperse. -​ For example, a canyon may create a barrier for small rodents, but not birds, coyotes, or pollen EVIDENCE OF ALLOPATRIC SPECIATION -​ 15 pairs of sibling species of snapping shrimp (Alpheus) are separated by the Isthmus of Panama -​ These species originated 9 to 13 million years ago, when the Isthmus of Panama formed and separated the Atlantic and Pacific waters SYMPATRIC (“SAME COUNTRY”) SPECIATION In sympatric speciation, speciation takes place in geographically overlapping populations. ALLOPATRIC AND SYMPATRIC SPECIATION: A REVIEW -​ In allopatric speciation, geographic isolation restricts gene flow between populations -​ Reproductive isolation may then arise by natural selection, genetic drift, or sexual selection in the isolated populations -​ Even if contact is restored between populations, interbreeding is prevented -​ In sympatric speciation, a reproductive barrier isolates a subset of a population without geographic separation from the parent species -​ Sympatric speciation can result from polyploidy, natural selection, or sexual selection PHYLOGENY AND SPECIATION EVOLUTIONARY CLASSIFICATION -​ Phylogeny = the study of evolutionary relationships -​ Biologists now group organisms into categories that represent evolutionary descent (and not just physical similarities) OVERVIEW: INVESTIGATING THE TREE OF LIFE -​ Evolutionary theory is so important to modern biology that it is how biologists organize the modern world -​ Phylogeny is the evolutionary history of a species or group of related species usually organized into a phylogenetic tree -​ Phylogenetic trees and cladograms arrange organisms based on common ancestry and shared characteristics HOW TO READ A CLADOGRAM -​ This diagram shows a relationship between 4 relatives -​ Relatives share a common ancestor at the root of the tree -​ The older organism is at the bottom of the tree -​ The four descendants at the top of the tree are DIFFERENT species. This is called SPECIATION. -​ Branches on the tree represent speciation -​ The event that caused speciation is shown as a fork on the tree HOW TO READ A CLADOGRAM -​ Species B and C each have characteristics that are unique only to them -​ But they also share some part of their history with species A. This shared history is the common ancestor. MONOPHYLETIC VS. PARAPHYLETIC VS. POLYPHYLETIC GROUPS  -​ A true clade is a monophyletic group that contains a common ancestor and all of its descendants. -​ A paraphyletic group is one that has a common ancestor but does not contain all of the descendants. -​ A polyphyletic group does not have a unique common ancestor for all the descendants PHOTOSYNTHESIS PURPOSED AND PROCESS OF PHOTOSYNTHESIS/PLANT LIFE REMEMBER WHAT PLANTS NEED… Photosynthesis. -​ Light reactions -​ Calvin cycle ​ Light ← sun ​ H20 ← ground ​ CO2 ← air A SECOND LOOK AT STOMATA Gas exchange. -​ CO2 in → for Calvin cycle -​ O2 out → from light reactions -​ H2O out → for light reactions CONTROLLING WATER LOSS FROM LEAVES Hot or dry days.  -​ Stomata close to conserve water -​ Guard cells +​ Gain H2O = stomata open +​ Lose H2O = stomata close -​ Adaptation to living on land, but… CREATES PROBLEMS CLOSED STOMATA Closed stomata leads to -​ O2 builds up (from light reactions) -​ CO2 is depleted (in Calvin cycle) ​ Causes problems in Calvin cycle INEFFICIENCY OF RUBISCO: CO2 VS 02 Rubisco in Calvin cycle -​ Carbon fixation enzyme +​ Normally bonds C to RuBP +​ Reduction of RuBP +​ Building sugars -​ When O2 concentrations is high +​ Rubisco bond O to RuBP +​ O2 is alternative substrate +​ Oxidation of RuBP +​ Breakdown sugars CALVIN CYCLE WITH O2 IMPACT OF PHOTORESPIRATION Oxidation of RuBP -​ Short circuit of Calvin cycle -​ Loss of carbons to CO2 +​ Can lose 50% of carbon fixed by Calvin cycle -​ Decreases photosynthetic output by siphoning off carbons +​ No ATP (energy) produced +​ No C6H12O6 (food) produced -​ If photorespiration could be reduced, plant would become 50% more efficient +​ Strong selection pressure REDUCING PHOTORESPIRATION Separate carbon fixation from the Calvin cycle. -​ C4 plants +​ Physically separate carbon fixation from Calvin cycle +​ Different enzyme to capture CO2 ​ PEP carboxylase stores carbon in 4C compounds -​ CAM plants +​ Separate carbon fixation from Calvin cycle by time of day +​ Fix carbon (capture CO2) during night ​ Stores carbon in organic acids +​ Perform Calvin cycle during day C4 PLANTS A better way to capture CO2 -​ Before Calvin cycle, fix carbon with enzyme PEP carboxylase +​ Store as 4-C compound -​ Adaptation to hot dry climates +​ Have to close stomata a lot +​ Different leaf anatomy -​ Sugar cane, corn, other grasses… C4 PLANTS C4 PHOTOSYNTHESIS Physically separated carbon fixation from the Calvin cycle. -​ Outer cells +​ light reaction & carbon fixation +​ pumps CO2 to inner cells +​ keeps O2 away from inner cells ​ away from Rubisco -​ Inner cells +​ Calvin cycle +​ glucose to veins CAM (CRASSULACEAN ACID METABOLISM) PLANTS Different adaptations to hot, dry climates -​ Succulents, some cacti, pineapple -​ Separate carbon fixation from Calvin cycle by time +​ Close stomata during day +​ Open stomata during night -​ At night, open stomata & fix carbon in “storage” compounds  +​ Organic acids: malic acid, isocitric acid -​ In day, close stomata & release CO2 from “storage” compounds to Calvin cycle +​ Increases concentration of CO2 in cells C4 VS CAM SUMMARY Solves CO2/O2 gas exchange vs. H2O loss challenge.