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Biology 20 Unit 20B: Ecosystems and Population Change 1 Biology 20 Unit 20B: Ecosystems and Population Change Chapter 4: Characteristics of Ecosystems 4.1 Interactions within Ecosystems ecology: study of interactions between organisms and their living and non-living environment at the level of a single organism abiotic factors: a non-living factor that influences an organism - sunlight and temperature biotic factors: a living factor that influences an organism - amount of food or mates Ecotones and Biodiversity sharp boundaries organisms can move back and forth from one ecosystem to another grey area between ecosystems where organisms from both ecosystems interact with each other - contain species from both bordering ecosystems - contain greater biodiversity (more species) than either ecosystem greater biodiversity ecosystems are less fragile more prey for predators since it is a fusion of two ecosystems Roles in Ecosystems niche: organism’s role in an ecosystem it’s place in the food web it’s habitat it’s breeding area time of the day at which it is most active ecological 2 Biology 20 Unit 20B: Ecosystems and Population Change higher the number of different niches in an ecosystem, the more organisms will be found more biodiversity in a natural forest than a planted forest Competition for Niches new species that enters an ecosystem causes a disturbance - exotic species: not a native species to an ecosystem animals can move into an out of ecosystems plant seeds are carried by the wind or animals transport them to new areas - a new route in an area can open up, allowing organisms that were separated to mix can create a new evolutionary species new species comes into the niche to compete with one or more of the species already in the ecosystem Introduction of Exotic Species new species caused by human introduction is one of the main causes of species depletion and extinction (loss of habitat is second) ecosystem lacks the natural population controls of the introduced species - no predators or disease giving the species an advantage over the native species - native species cannot compete successfully for space, food or reproductive sites 3 Biology 20 Unit 20B: Ecosystems and Population Change Example: in 1935 the Cane Toad was introduced into Australia, in an attempt to rid sugarcane fields of cane beetles. Native to South and Central America and thrives in Australia since it is poisonous and has no predators or disease to kill them. 4.2 Terrestrial and Aquatic Ecosystems biome: large geographical region with a specific range of temperatures and precipitation plants and animals are adapted to those conditions of temperature and precipitation biomes have a particular dominant species - taiga biomes has coniferous trees - grassland biome has prairie grasses each biome contains many different ecosystems - each defined by different biotic and abiotic factors Canada has four major terrestrial biomes Tundra, taiga, grassland and temperate deciduous forest as well as two major aquatic biomes - freshwater: lakes, rivers and pond ecosystems - saltwater: marine and ocean ecosystems 4 Biology 20 Unit 20B: Ecosystems and Population Change 5 Biology 20 Unit 20B: Ecosystems and Population Change Terrestrial Ecosystems Alberta’s terrestrial ecosystem are found within two major biomes: taiga and grassland Ecosystems of the Taiga Biome also called the boreal forest can be found from Northern Alberta and along the Rocky Mountains - can be found in every province in Canada - 80% of all our forested region are taiga dominated by conifers well adapted to the warm, moist summers and cold, dry winters thin needle-like leaves provide less surface area for water loss thick cuticle of wax coats the needles prevents water loss and protection against frost damage pyramid shape of the tree and the flexible branches shed the crushing weight of a heavy snowfall tiny needles trap little snow - amount of sunlight varies depending on the height above the ground canopy: upper layer of vegetation in a forest usually mature trees (pine and spruce) suitable food source for only 50 species of birds including seed-eaters that have a strong, thick beaks capable of cracking cones forest floor is in almost continuous shade since little sunlight filers through the canopy - forest floor has shade-loving plants (shrubs, mosses and ferns) animals have to have effective camouflage - primary consumers: moose, voles and white-tailed deer available shelter is also determined by these shade loving plants - predators: black and grizzly bears, weasels, owls and wolverines 6 Biology 20 Unit 20B: Ecosystems and Population Change Muskeg Ecosystems climate is the average conditions of temperature and precipitation - warmer ground temperatures increases decomposition of organic matter results in good soil decomposition of needles produces acidic soil certain plants will only grow in acidic soils black spruce trees - colder climate in the north has a permafrost layer beneath the soil soil never melts permafrost: permanently frozen soil - rain and melted snow cannot drain away and is absorbed by the decomposing plants and peat moss muskeg: soil above the permafrost that is swampy or boggy in summer supports different organisms than are found in a conifer forest ecosystem decomposition of plant and animal matter is slow - low temperatures limit the growth and reproduction of soil bacteria and fungi - limits the amount of organic matter in the soil plants best for this ecosystem grow close to the ground have fibrous root systems that anchor the stunted conifers plants include: lichens, mosses, tall grasses, small shrubs and stunted conifers numerous pools provide abundant water for plants and animals - ideal breeding conditions for black flies and mosquitoes - supports come larger animals like caribou Ecosystems of the Grassland Biomes black earth is the most fertile in the world - short lived grasses have deep roots that provide a large biomass for decomposition - warm temperature for rapid decay and a rich layer of humus - grass length controlled by precipitation - have only one layer to support the biotic community limits the diversity and number of organisms Alberta’s grasslands include rough fescue, wheat grass and spear grass 7 Biology 20 Unit 20B: Ecosystems and Population Change - primary consumers: deer, squirrels and rabbits Deciduous Forest Ecosystems edges are dominated by trees - before it turns into the taiga aspen, balsam poplar and birch are the most common trees - require low amounts of water than coniferous trees - found in areas where rain is sporadic between the true grasslands and the taiga - deciduous trees can be found around rivers, lakes and ponds warmer temperatures and more precipitation - large amount of humus from the leaves provide a rich soil in deciduous forests early spring, most of the sunlight reaches the forest floor and the understory - understory: below the canopy layer consisting of shrubs and smaller trees summer the canopy is full leaf and only 6% of sunlight reaches the understory - undergrowth is well established - broad leaves of the deciduous trees maximize light capture for photosynthesis, promoting rapid growth deciduous forests support great diversity of animals - thick layer of leaf litter provides an ideal environment for many types of insects - insect-eating birds and mammals live in deciduous forest ecosystems fly-catchers and shrews - rich vegetation of the understory shrubs and lower branches supports primary consumers like deer and moose home to many species of birds and some climbing mammals 8 Biology 20 Unit 20B: Ecosystems and Population Change Name Taiga Ecosystems Abiotic Factors northern and central Alberta forests changeable weather soil contains some water and is acidic precipitation: 50-250 cm/a Muskeg Ecosystems Grassland Ecosystems Deciduous Forest Ecosystems cold temperature short growing season permafrost layer beneath soil low precipitation: 50-150 cm/a central and southern Alberta increased sunlight and warmer temperatures than muskeg or boreal forest ecosystems rich fertile soil precipitation: 25-100 cm/a central Alberta increased sunlight and warmer temperatures than muskeg or taiga forest ecosystems rich fertile soil precipitation: 75-250 cm/a 9 Biotic Community black and grizzly bears wolverines weasels moose deer grouse owls spruce and pine shrubs, ferns, mosses and lichens black bear caribous ptarmigans rapidly flowering plants mosses and lichens bison deer rabbits hawks yellow-bellied sapsuckers fescue grasses grasshoppers black bears weasels moose deer woodpeckers deciduous trees shrubs Aquatic Ecosystems water covers 2/3 and 97% is salt water supply freshwater through evaporation water based communities as either freshwater or marine water marine waters include oceans, coastlines and some land surfaces freshwater is on land surfaces - ponds, bogs, sloughs and other types of wetlands estuary: place where rivers enter the ocean where the water is brackish brackish: mixture of fresh and salt water Biology 20 Unit 20B: Ecosystems and Population Change 10 Lake Ecosystems amount of light available, water temperature and oxygen levels can vary watershed: land that drains toward a lake or other body of water Littoral zone edge around a lake or pond where the water is shallow - determined by the depth of the lake and the slope of the lakebed - ends when there are no more rooted plants bulrushes and water lilies grow where the water is shallow - permits the growth of aquatic emergent vegetation most productive part of the lake - algae and plants take advantage of the sunlight to carry out photosynthesis Limnetic Zone open water area of a lake where photosynthesis can occur - extends downward to a depth at which there is insufficient light for photosynthesis plankton organisms are present - includes autotrophic and heterotrophic microorganisms heterotrophic plankton (invertebrate animals) feed on autotrophic plankton (tiny plants and algae) - both kinds of plankton are food consumers in the higher trophic levels fish, tadpoles and birds Profundal Zone region of a lake where there is not enough light for photosynthesis - no photosynthetic plants - usually not found in ponds only source of nutrients is decaying matter falling from the limnetic zone - benthic detritus feeders: detritus is slowly broken down by bacteria or consumed by otherbottom dwelling invertebrates and fish - benthos: bottom of any body of water in the benthic zone extremely low levels of oxygen since bacteria uses oxygen to decompose the detritus - absence of sunlight and plants to replenish the oxygen causes an extreme depletion of oxygen - only larger organism that can survive in low oxygen levels survive includes invertebrates and very few fish species such as carp Biology 20 Unit 20B: Ecosystems and Population Change 4.3 Factors Affecting Ecosystems Factors Affecting Terrestrial Ecosystems quality and amount of soil are critical for the size and health of the plant community directly affects biodiversity of the ecosystem series of layers, each with a distinct colour and texture move deeper down the less organic matter that is present litter: composed of partially decomposed leaves or grasses - acts like a blanket limits the temperature variations in the soil reduces water loss by evapouration topsoil: composed of small particles of rock mixed with subsoil Soil bedrock regions all function as a system each ecosystem has independent biotic and abiotic factors - can limit the size of the populations - can determine the number of species that can survive in each ecosystem topsoil terrestrial 11 Biology 20 Unit 20B: Ecosystems and Population Change 12 humus - humus: black decaying plant and animal matter - contains a rich supply of minerals and other nutrients plants require to grow - air and water spaces are between the soil particles decomposing bacteria requires oxygen less oxygen the slower decomposition subsoil: usually containing more rock particles and less organic matter than the topsoil - lighter in colour since there is a lack of humus - contains large amounts of minerals aluminum, iron and phosphorous bedrock: composed of rock and marks the end of the soil can be acidic, basic (alkaline) or neutral pH of the soil is determined by the nature of the rock and the plants that grow in it - decomposing matter can cause an accumulation of acid in the soil - acidity of the rain, snow and groundwater - humans burning fossil fuels can increase the soil acidity releases SO2 and NOx into the air creates acid rain/snow when combine with water drops Available Water overall climate of the area determined by the amount and type of precipitation amount of available water is determined by how long it stays in the upper layer of the soil how much it collects beneath the soil collects in lakes, rivers, ponds and seepage into porous rocks below the soil groundwater: water in the soil or rock below the Earth’s surface water table is the area between the saturated soil and unsaturated soil leaching: water seeping down, collecting organic matter and minerals from the soil, deeper into the soil serious problem since it remove nutrient that plants need to grow branching roots extend deep into the soil and help pump minerals and other chemicals back to the surface Temperature overall climate of the region can vary significantly affecting both biotic and abiotic factors - hot temperatures can evaporate water faster plants need longer roots - colder temperature hold water in the soil longer Biology 20 Unit 20B: Ecosystems and Population Change plants need shorter roots Sunlight ecosystems close to the equator receive constant amounts of light throughout the year northern and southern hemispheres have varying amounts of light throughout the year plants in the ecosystem can also cause the sunlight to be blocked from other plants or organisms Factors Affecting Aquatic Ecosystems Chemical Environment includes the type of water freshwater ecosystems seldom survive in saltwater ecosystem and vice versa amount of oxygen dissolved in the water organisms can only get their oxygen from the water amount of oxygen depends on the temperature of the water, pressure and salt naturally occurring minerals are also found in the water phosphorous and nitrogen also chemical pollutants can be in the water Temperature and Sunlight ecosystems near the surface of an ocean obtains more light and has warmer temperatures than one deeper life can exist without light Water Pressure 800 times more dense than air making it harder to move through restricted by the amount they can move up and down at 10 m pressure is double what it is at surface - pressure increases by 100 kPa for every 10m of depth Seasonal Variation in Canadian Lakes causes significant changes in abiotic factors in freshwater ecosystems water cools it become more dense water below 4C starts becoming less dense - ice floats forming a layer of cold on top of warm - bottom of the lake is at the lowest temperature of 4C 13 Biology 20 Unit 20B: Ecosystems and Population Change Winter Stagnation ice prevents the dissolving of atmospheric oxygen bottom 4C to the top water 0C wind-blown ice allows light to penetrate for photosynthesis - fish die-off: no light decreases oxygen to a level that cannot support the biological life Spring Overturn winds, rain and storms mix oxygen into the water - increases the rate of dissolving atmospheric - increases the surface area by oxygen stirring-up the water surface water increases to 4C and sinks to carry oxygen to the less dense water bloom: rapid growth of blue-green algae from the release of nutrients in decaying matter 14 Biology 20 Unit 20B: Ecosystems and Population Change Summer Stagnation develops temperature different (thermal) layers - epilimnion: upper lake water layer that heats up in the summer warmer the water the less oxygen it will hold - thermocline: separating zone from the epilimnion and hypolimnion water temperature drops from warm to cold - hypolimnion: lower lake water layer that maintains a constant cold temperature lack of mixing blocks the movement of oxygen into the hypolimnion lower temperature holds oxygen more efficiently in the water Fall Overturn renewed oxygen levels by breaking down the thermal layers reversal of spring overturn 15 Biology 20 Unit 20B: Ecosystems and Population Change 16 4.4 Limits on Populations and Communities in Ecosystems Biotic Potential biotic potential: maximum number of offspring that a species could produce with unlimited resources Limiting Factors factors in the environment can prevent populations from attaining their biotic potential food, water, territory and pollution and other toxic chemicals fluctuations caused by more than one factor occur naturally in an ecosystem Biology 20 Unit 20B: Ecosystems and Population Change Carrying Capacity maximum number of individuals of a species that can be supported by an ecosystem is determined by the availability of resources - food and water - can exceed the carrying capacity of the ecosystem for a short time population fluctuate because of an interaction of the many biotic and abiotic limiting factors communities are often stable Limits of Tolerance law of minimum: the nutrient is the least supply is the one that limits growth Shelford’s law of tolerance: organism can survive within (tolerate) a particular range of an abiotic factor Above and below the range cannot survive He greater the range of tolerance, the greater the organisms ability to survive 17 Biology 20 Unit 20B: Ecosystems and Population Change 18 Density-Independent and Density-Dependant Factors density-independent: a factor that affects members of a population regardless of population density fire and flood are naturally occurring events affect population regardless of size density-dependant: a factor that affects members of a population because of the population density food supply, water quality, sunlight, disease and territory Density-Independent Factors flood fire spraying with pesticides change in climate or temperature destruction of habitat drought Density-Dependant Factors food shortage competition for mates, breeding areas (habitat) disease caused by a microorganism or parasite introduction of an exotic species increased predation competition for water and other resources Biology 20 Unit 20B: Ecosystems and Population Change 19 Chapter 5: Evolution Importance of Adaptation two levels of biological diversity species diversity: number of different species genetic diversity: amount of variation of inherited traits between individuals of the same species no two organisms are exactly alike is the most important feature for all life – diversity all living things show similarities - all plants and animals share certain characteristics regardless of size, shape or level of complexity all share requirements for energy, basic cell structure and function plus adaptation to a particular habitat adaptation: inherited trait or set of traits that improve the chances fro survival and reproduction of organism all living organisms are adapted in appearance, behaviour, structure and mode of life make them well suited to survive in a particular environment - adaptations are specific for that organism in that environment theory of evolution explains why organism similar in biochemistry and molecular biology are so different in form and function evolution: cumulative changes in characteristics of populations of organisms in successive generations - living things change over a series of generations - does not refer to individual change or development Types of Adaptation Structural Adaptations most organisms show clear structural adaptations to their environment can be modifications to pentadactyl limb or leaves - forelimb and five digits adaptations in humans, seal an bats humans to grasp and hold things longer in bats to lengthen and support the wing for flying shorter in seals to support the flipper for swimming Biology 20 Unit 20B: Ecosystems and Population Change 20 - plant leaves and structure to capture insects Venus fly traps leaves to capture prey pitcher plant leaves are shaped like a jar to capture insects these adaptations usually arise from plants not receiving enough nutrients or light for photosynthesis live in bogs and wetlands where soil nitrogen is poor Physiological (Biochemical) Adaptations enables the plant to produce chemicals for the digestion of its prey is less obvious production of chemicals for sexual attraction and alarm signals - pheromones: chemicals secreted by organisms to influence the behaviour of other organisms a lot of physiological adaptations involve specialized enzymes that control body functions - temperature, respiration, digestion, circulation and blood clotting, muscle and nerve coordination - enzymes: special protein structures that regulate chemical reactions Behavioural Adaptations key factor in keep organisms alive and enabling them to reproduce - southward migration of the Canada goose - hibernation of certain animals - storage of nuts by squirrels most organisms respond to stimuli and may show adaptations in the way they behave - protozoan’s such as amoebas and hydras respond quickly to touch by moving away react to temperature changes and chemical substance in water - some organism may move away from or towards the stimulus depends on the stressfulness of the situation - earthworms will react to touch, light and chemicals in the soil react to light by burrowing in the soil and only come out at night plants are controlled by chemical hormones - tropism: orientation of plants according to some stimulus phototropism is plants “bending” toward the light 5.1 Classification of Organisms Taxonomic Systems taxonomy: science of classification according to the inferred (presumed) relationships among organisms Biology 20 Unit 20B: Ecosystems and Population Change 21 classification systems have two main purposes 1. identify organisms 2. provide a basis for recognizing natural groups of living things classification systems are artificial - developed by scientist to help deal with diversity of life and relationships among organisms Carl Linnaeus (1707 – 1778): Swedish botanist who developed the taxonomy system that is still used today based on the physical and structural features - more features that organisms have in common the closer the relationship binomial nomenclature: naming organisms by using two names - Genus: includes several species first letter is always capitalized - species: group of organisms that look alike and can interbreed under natural conditions to produce fertile offspring two name system has an advantage by indicting similarities in anatomy, embryology and evolutionary ancestry - North American black bear: Ursus americanum - grizzly bear: Ursus horribilis - giant Alaskan brown bear: Ursus arctos - polar bear: Ursus maritimus phylogeny: history of evolution of a species or group of organisms represented by a phylogenetic tree (evolutionary tree) - tree starts from the most ancestral form and includes branching that lead o all of its descendants Biology 20 Unit 20B: Ecosystems and Population Change dichotomous key: two-part key used to identify living things constructed so a series of choices must be made each new choice leads to a new branch of the key choices are correct – leads to the name of the organism being identified 5.2 Evidence of a Changing Earth Evidence from Fossils 22 Biology 20 Unit 20B: Ecosystems and Population Change 23 palaeontology: is the study of fossils ~ 250 000 fossilized species have been found fractional representation of the overall population that existed fossils offer direct evidence of the pathways taken by living organisms in their evolutionary history (phylogeny) fossils: represent species that have become extinct living fossils: fossils from species that have changed very little over a long period of time fossils alone do not provide absolute proof of evolution can construct convincing arguments for the process of evolution How are Fossils Formed? fossils can be created by a number of different ways hard parts of organisms resist the action of weathering for long periods, particularly in dry environments - teeth, bones and shells some soft tissues of extinct organisms have been preserved - mammoths entirely intact preserved by the deep freeze process over 10 000 years ago impressions or imprints of plants and animals - tracks made in soft mud and the fecal material of animals organism become entrapped and embedded in amber - insects in amber amber is a hardened gum given off by trees - animals, birds, mammoths, horses and camels in the old tar pits cell cavities and intracellular spaces of the skeletal material of plants or animals are replaced by mineral matter silica, calcite or iron compounds makes a petrified structure most fossils are found in sedimentary rocks formed when sand and rock particles are laid down usually at the bottom of oceans and lakes - new layers are formed over older ones and the layers compress and harden Biology 20 Unit 20B: Ecosystems and Population Change Dating the Past 1000 years to form 30 cm of sedimentary rock thickness of the rock layer can determine the approximate age - must use its location above and below other rock layers radioactive dating has been used more recently to determine the age of fossils and rocks measurements of decay of radioactive isotopes (geological clock) - absolute age of the Earth with great precision - changes a particular atom (parent isotope) into daughter isotopes radioactive potassium-40 decays into agron-40 or calcium-40 radioactive uranium-238 decays into lead-206 - half-life: amount of time for half the sample to become stable not affected by temperature, moisture or other environmental conditions radiometric dating: technique used to determine the age of a rock or fossil determine both age of the earth and the time that the first life forms appeared - earth was formed 4.5 billion years ago and life first appeared about 3.8 billion years ago - fossils of more recent origin represents more complex organisms oldest parts of the fossils record contains simple organisms time difference between the two groups is great, the difference between the groups is great gaps occur in the record when the layer does not contain fossils of certain kinds - found in layers both before and after the gap - gaps are called “missing links 24 Biology 20 Unit 20B: Ecosystems and Population Change 5.3 Evidence for Evolution From Biology Evidence from Anatomy observed through living organisms links between existing forms and their ancestors - physical anatomy and genetic make-up - supports theory of modern species evolved from ancestral species Homologous and Analogous Structures anatomical evidence reveals structural similarities among organisms organism with similar structures evolved from a common ancestor becomes increasing obvious homologous structures: similar structures and origin but different functions - same origin as forearm or leg buds bat wing, whale flipper, cat leg and human arm all share similar bone arrangements all have different functions all have the same pattern of early growth analogous structures: similar in function and appearances but not in origin - similar functions but are quite different anatomically suggests that they do not have the same evolutionary origin wing of a bird and of a butterfly or insect Butterfly wing 25 Biology 20 Unit 20B: Ecosystems and Population Change Embryology study of organisms in the early stages of development valuable insight into the process of evolution similarity of the embryos is due to their evolution from a common ancestor young forms of these organisms resemble the young of the related species farther the species the early the break in embryological development - salamander and chicken are connected but break away from the pig and human longer the embryos look similar the closer the species are Physiological Evidence physiological studies show the similarities among organisms study of the function of any part of an organism - wastes excreted from the kidney s of birds and reptiles have the same chemical make-up - certain hormones from sheep and pigs can be injected into humans insulin for diabetes is obtained from cow or pig pancrease Vestigial Feature and Anatomical Oddities vestigial features: rudimentary structures that sere no useful function present in all species and provide the most compelling evidence for evolution once served as a function in ancient ancestor - some modern whale and snake species have vestigial hip and leg bones evidence of evolution from fourlegged ancestors - humans appendix evolved from a second stomach in ancient humans - mammals with vestigial toe bones elevated above ground - some beetle have winds trapped beneath fused covers 26 Biology 20 Unit 20B: Ecosystems and Population Change 27 - blind cave salamanders have empty eye sockets evolved from salamanders with fully functional eyes Evidence from Biochemistry many structures are made up of proteins such as muscle and skin cells proteins are made up of long chains of amino acids - each type of protein has a unique number and sequence of amino acids - many species posses similar proteins overtime proteins in similar species become increasing different hemoglobin, oxygen carrying molecule, in all invertebrates varies between species that are less similar suggests that hemoglobin molecules evolved to have different characteristics a variety of chemical analysis techniques have been used to show that all organism share similar DNA molecules DNA (deoxyribose nucleic acid): heredity material that determine characteristics or traits are passed onto the next generation - composed from 4 nucleotide bases that are varied in number and order adenine (A) – thymine (T) cytosine (C) – guanine (G) - genes: segment of DNA that performs a specific functions or particular traits biologists have discovered homologous and vestigial anatomical features, geneticists have found homologous and vestigial genes in DNA - found in all species - humans have defective genes that would allow us to make our own vitamin C lost the ability and need to make our own we still poses the instructions to do so species from different orders are compared the difference in their DNA structure is greater than when species within the same genus are compared Biology 20 Unit 20B: Ecosystems and Population Change Evidence from Artificial Selection artificial selection: breeding used to alter appearance, behaviour and chemical make-up of plants and animals select individuals with the desired traits and breed them so the offspring will have the same inherited trait - breeds today have been selected for over hundreds of generations cabbage, broccoli, cauliflower and ornamental kale are all the same species - farmers selected traits for a single species of sea cabbage produce dramatic changes over a short period of time supports more dramatic changes in nature over millions of years and countless generations 5.4 The Making of a Theory – Accounting for the Evidence Early Beliefs before the 18th century species were thought of as “fixed” from the first time they appeared on Earth the second half of the 18th century a number of scholars began to speculate and speak out on the issue of evolution Pierre Louis de Maupertius - French mathematician - multiplication of species was a result of accidental recombination of elementary particles leads to offspring that are different from their ancestral form genes in modern biological terms Georges-Louis Leclerc de Buffon - leading naturalist - two hypothesis to explain the world distribution of plants and animals “creation of species” did not occur in one single place but in a number of “centers of creation” (form hybrids) species were not created in a perfect state but underwent modifications over time Carl Linnaeus (1760) - Swedish botanist and the founder of biological nomenclature Erasmus Darwin (1794) - Charles Darwin’s grandfather 28 Biology 20 Unit 20B: Ecosystems and Population Change - physician and naturalist - all life had developed from a single source Lamarck’s Theory Jean-Baptiste de Lamarck (early 1800’s) first theory of evolution that included a mechanism spontaneous generation: belief that living things arose from non-living matter - new, very simple species were continually being created and gradually became more complex organisms have an imaginary “force” or “desire” to change themselves for the better - must be able to produce new parts to satisfy the needs in order to become better adapted to the environment use and disuse of certain structures could be passed off to the offspring - more the structure is used the stronger the parts one generation of the giraffe might have obtained food from higher trees continual stretching of the neck would lead to a slight elongation over time trait was passed onto offspring and generations later the neck progressively became longer inheritance of acquires characteristics: “Lamarckism” is the false concept of inheritance of features acquired during the life of an individual 29 Biology 20 Unit 20B: Ecosystems and Population Change 30 Darwin’s Theory Charles Darwin (1809-1882) 1831 set sail on HMS Beagle to travel around the world and returned in 1836 came back with questions and observations 1. unusual fossils that resembled a variation of sloths and armadillos living in the same region - inference: living forms might have descended from the fossilized species 2. species in African tropic did not resemble the species in the South American tropics - resembled the species living in cooler parts of South America - inference: each landmass acted like an isolation nursery allows each species to evolve independently 3. harsh landscape of the Galapagos Islands were home to 13 very similar species of finches - found nowhere else on Earth but resembled a species living 1000 km off the coast of South America - inference: all had evolved from a single species that had arrived from Galapagos from South America 4. fossil deposits of corals at the elevation of 3000 m in the Andes Mountains - inference: geological forces over a vast period of time could account for the fossils in the mountains through artificial selection discovered that all species possessed inherited variations that could be selected to change the traits of the species in desirable ways Biology 20 Unit 20B: Ecosystems and Population Change published On the Origin of Species by Means of Natural Selection in 1859 based on a simple set of observations and logical reasoning - observed: all species exhibited inherited variations - reasoned: variations allowed some individuals to be better adapted to survive and reproduce that other - inherited traits provided the survival advantage and would become more common in the population Natural Selection differential reproductive success of individuals caused by variations in their inherited characteristics can be divided into six distinct ideas: 1. variation: differences amount traits occur among members of the same species no two individuals are exactly alike - variations including acquired variations are passed on from one generation to the next 2. overproduction: number of offspring produced by a new species is greater than the number that can survive, reproduce and live to maturity 3. populations of species are stable in size 4. struggle for existence (competition): organisms of the same species and those of different species must compete for limited resources - food, water and place to live 5. survival of the fittest (natural selection): individuals of a species with traits that give them an advantage are better able to compete, survive and reproduce - all others die without leaving offspring - nature picks who survives, the well adapted one to their environment - not random 6. origin of new species by inheritance of successful variations (speciation/evolution): new species arise by accumulation of inherited variations 31 Biology 20 Unit 20B: Ecosystems and Population Change 32 - type is produced that is significantly different from the original, a new species has arisen 5.5 Sources of Inherited Variation Mutations DNA is founding the chromosome of cells composed of 4 nucleotide bases in a sequence that forms a code - translated by the cell gives the organisms the specific inherited traits - genes are segments of DNA that code for specific traits each gene ahs a specific DNA sequence DNA is like a blueprint for a particular individual organism DNA will remain the same throughout its life unless mutated mutations: random changes in DNA and provide continuous supply of new genetic information - caused by environmental factors (chemical or radiation) or arise from errors when the cells use or make copies of the DNA molecule - loss or duplication of an entire section of DNA or simple changes to the DNA sequence - relatively rare in individuals ranging from one new mutation per sex cell large populations reproduced over many generations gives rise to a substantial number of mutations effects of mutations depend on the what DNA sequence is altered and how it is affected neutral mutation: has no effect on the organism - fitness: organism’s reproductive success harmful mutation: reduces the organisms fitness - selected against the species and do not accumulate over the generations beneficial mutation: enhances an organisms fitness - selected for and may accumulate over the generations - not many mutations in nature are beneficial, majority are harmful or neutral Biology 20 Unit 20B: Ecosystems and Population Change 5.6 Speciation and Evolution Speciation speciation: formation of new species species: a group of similar organisms that can interbreed and produce fertile offspring in their natural environment - population of individuals who are reproductively isolated not capable of breeding with individuals of other species under natural conditions there are more species present today than in the past two ways in which a new species can arise: populations or parts become isolated and must adapt to conditions selective pressures also vary where species are not created instantly but evolves over a long period of time Geographic Isolation separation caused by physical obstacles such as mountains, canyons or water - barriers created by humans such as damns or canals - into two or more groups that are isolated from each other mutations that occur are not shared with the other population natural selection works on the separated groups resulting in inherited differences between the two populations genetic flow between isolated and the main group ceases - individuals over time become so different they cannot interbreed different adaptations in separate environments different gene frequencies and different mutations over a long time Reproductive Isolation geographic isolation can lead to reproductive or genetic isolation - both populations split and live in the same geographic region over a short time still gives rise to speciation - reproductive isolation occurs when organisms in a population can no longer mate and produce offspring 33 Biology 20 Unit 20B: Ecosystems and Population Change - still occurs even after the barrier has been removed contributors are mating habits and courtship patterns - seasonal differences in mating - inability of sperms to fertilize eggs - even if fertilized genes and chromosomes cannot interact The Rate of Evolution theory of gradualism: idea that speciation takes place slowly some fossils support this with small changes in species theory of punctuated equilibrium: idea that species evolve rapidly followed by a period of no or little change supported by the fossil record three main ideas 1. many species evolve very rapidly in evolutionary time 2. speciation occurs in small isolated populations - intermediate fossils are very rare 3. after initial burst of evolution, species are well adapted to their environment - do not change significantly over long periods of time Macroevolution: Diversification and Extinction trend of increase diversity has been interrupted by “extinction events” 34 Biology 20 Unit 20B: Ecosystems and Population Change 35 divergent evolution: evolution into many different species that are vaguely similar marsupial distribution in Africa, Australia and South America can be explained by continental drift that followed the Pangaea break-up - similar marsupials developed in different contraries but with similar environments convergent evolution: development of similar forms from unrelated species due to adaptation to similar environments mammals which did not appear until after the break-up of Pangaea are limited in their distribution each type of mammal tends to be unique to a specific continent