Gen Bio 1060 Week 15 Lecture Notes
Gen Bio 1060 Week 15 Lecture Notes Bio 1060
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This 11 page Class Notes was uploaded by Margaret Notetaker on Saturday April 30, 2016. The Class Notes belongs to Bio 1060 at Saint Louis University taught by Dr. Thole in Spring 2016. Since its upload, it has received 12 views. For similar materials see General Biology II in Biology at Saint Louis University.
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Date Created: 04/30/16
Margaret S Biology 1060 (General Biology II) Week 2 Notes Unit 4: Ecology 4-‐18-‐16 Community Ecology • Community ecology refers to interactions between different species in 1 geographic area • Interactions between species: symbioses o Mutualisms: both species benefit; the most common type of beneficial symbioses § Ex. Flowers can only reproduce with their pollinator’s help o Antagonism: one participant loses more than it gains § Parasitism (an organism lives inside of another and steals its nutrients, the host typically becomes ill) § Predation (one organism eats another, for example a bird [predator] eats a fish [prey]) § Herbivory-‐a form of predation (animal eating a plant) § Competition between species for resources (harmful to both species) • Niche: a combination of a species’ physical habitat and its ecological role in that habitat o Biotic and abiotic factors to niches o All species in the same habitat will have some difference in niches that allows them to avoid some kind of competition o The fundamental niche: larger than the realized niche, consists of any area that an organism could theoretically live o The realized niche: smaller than the fundamental niche, consists of anywhere an organism could actually live after taking into account competition and biotic factors • Competition: when niches overlap o Intraspecific competition: competition within individuals of a species o Interspecific competition: two species competing for one resource o Interference competition: (still interspecific competition): physical interactions (ex. Fighting) over access to resources o Exploitative competition: when the only interaction between species is when trying to use resource • The more similar a niche of 2 species, the stronger the competition (niche overlap), which can lead to o Competitive exclusion: when competitors cannot coexist, (Harry Potter and Voldemort: one cannot live while the other survives) which may then lead to: o Resource partitioning: subdivision of niche by organisms, which only occurs when the niches don’t overlap completely J.H. Connell’s Study of Barnacles • 2 species of barnacle: when they live together, one lives in higher tidal zone and the other lives in a lower tidal zone; but when the lower zone species is removed, the higher zone species expands its niche to fill both tidal zones Resource Partitioning • Resource partitioning can lead to character displacement, which is when the partitioning is so extreme that it leads to differences in phenotypes o Ex. Finches: allopatric (geographically separated); when 2 species are separate (allopatric) they have the same beak size, but when they are together (sympatric) one species has a shallower beak than the other o Ex. Anolis lizards: they are believed to have evolved originally from only a few species, but competition lead to tons of different species in the same niche (trees): now each species has a specific realized niche in a non-‐overlapping subset of the trees Predation • Predation is the consumption of one organism (prey) by another (predator), where prey is alive o Predators/carnivores typically synonyms o Grazers/herbivores typically synonyms • Presence of predators can influence competition Parasitism • Parasitism is the ecological interaction in which one organism benefits while the other is harmed o This is the most common feeding mode on Earth o It can be viewed as predation o Some nonphotosynthetic plants parasitize other photosynthetic plants by tapping into their roots o Parasitism also happens a lot in animals (like dogs and worms/ticks) Mutualism • An ecological interaction in which both species benefit • Sometimes one species relies on the other, and sometimes both rely on each other • Ex. Pollination, seed dispersal (seeds and animals that eat/excrete them), roots and nitrogen fixing bacteria, clown fish and sea anenomes • Facultative Mutualism: both organisms can live on their own, they just prefer to be near each other because they do well when they are together • Obligate Mutualism: either neither or one of the species can live on their own o Ex. of obligate mutualism: lichen composed of fungus and algae Commensalism • Commensalism is an ecological interaction wherein one organism benefits but the other has a neutral experience • Cattle egrets (a type of bird) live around cows, and as cows walk around and stir up bugs in the grass cattle egrets eat the bugs; the cattle egret benefits, and the cow neither benefits nor suffers Mutualism and Coevolution • Ex. aphids and bacteria (buchnera) have almost identical phylogenetic trees because their evolutionary histories have relied so much on the other due to their mutualistic relationship Summary: o (-‐) means that the organism suffers due to the ecological relationship o (+) means that the organism benefits due to the ecological relationship o (0) means that the organism does not suffer or benefit due to the ecological relationship • Competition o (-‐/-‐) • Predation, herbivory, parasitism o (+/-‐) • Mutualism o (+/+) • Commensalism o (+/0) 4-‐20-‐16 Community Ecology • Keystone species: a species that is not great in number, but that is vital to a community-‐that community would change drastically if the species were not there • Communities are constantly changing o Climate o Species invasion o Disturbances (things that are not the norm) • Species are affected by indirect effects sometimes o Ex. if 1 prey is preferred, that has a positive indirect benefit to the other prey in the area • All species are related to each other either directly or indirectly • Keystone species (a second definition): a species whose impact on the community or ecosystem is disproportionately large relative to its abundance o Ex. otters eat urchins which will otherwise overtake giant kelp forests where other animals live; without the otters, urchins take over and destroy the kelp and many other species will suffer; otters are keystone species o Ex. beavers construct dams that make lakes/ponds, which house many organisms; in this example, the beavers are the keystone species o Ex. carnivorous starfish eat mussels that eat small invertebrates; this allows invertebrates to survive, so when there are too many mussels they take over the entire ecosystem; carnivorous starfish are keystone species • Natural disturbances o Daily: treefalls, erosion, etc. o Seasonal: floods, fires, drought, etc. o Multiyear: landslides, fires, etc. o Decadal: hurricanes, severe drought, etc. o Centennial: climate change • Species richness tends to be highest when disturbances are relatively frequent • Succession: a community’s response to a disturbance o Moving back into a destroyed habitat and recolonizing o First organisms to come in are lichen and moss, followed by small invertebrates (r-‐strategists), soon after this happens the soil changes from rock to true soil due to plant interaction • Mt. St. Helen eruption: 1985, nothing left around it but patches of grass; in 2002, trees and bushes started to grow back • Primary succession: when organisms begin colonizing an area (substrate) that never had life on it o Ex. glaciers receding o Establishment: Immediately during primary succession, lichen secrete acid that breaks down rock and moss starts to grow with nitrogen fixing bacteria that prepare the soil for future plants o Facilitation: alder shrubs start growing o Inhibition: when the land is fully colonized and no other plants start growing there • Secondary succession: the existing community is disturbed, but some organisms still remain (ex. fire) • Intermediate Disturbance Hypothesis: o The graph with disturbance frequency on the x-‐axis and species diversity on the y-‐axis is a bell curve; a moderate amount of disturbances is optimal for biodiversity Ecosystem Ecology • Ecosystem Ecology: Multiple communities of organisms that live in an area and the chemical and physical environment that surrounds them • 4 Components of Ecosystem Ecology: o Abiotic environment o Primary producers o Consumers o Decomposers o All of these components are linked by the movement of nutrients and the transfer of energy • Energy FLOWS, Nutrients CYCLE o The sun shines on primary producers, which feed the consumers and the decomposers, which feed on each other, and all are influenced by abiotic factors o The flow of energy is unidirectional and noncyclic; only the nutrient cycle is cyclic o There is dissipation of energy at every trophic level; but there is no dissipation of nutrients at any level o Energy pools don’t exist on earth; but nutrient pools do • Obtaining Matter and Nutrients o Producers are autotrophs (typically plants) o Consumers are heterotrophs (herbivores, predators, parasites) o Decomposers return carbon and minerals to the earth (typically fungi, etc.) • Energy Flow in Ecosystems o Productivity: the rate of synthesis of organic matter o Primary productivity: plants, algae, bacteria (Trophic Level 1) o Secondary productivity: heterotroph level, consumers (Trophic Levels 2-‐4) § Energy flow is lessened from one level transfer to the next, because some is always lost as heat: only about 10% of available energy is converted to the next level (energy flow is inefficient) § Ex. 1000 kg of grass (primary producers) à 100 kg grasshoppers (herbivores/primary consumers) à 10 kg lemmings (predators/secondary consumers) à 1 kg eagles (predators/tertiary consumers) o Respiration is the rate at which primary producers break down organic compounds • Food Webs: the arrows in food webs show the transfer of energy; all arrows move away from grass and upwards towards the highest level of consumers o Primary producers get their energy from the sun, and their nutrients from decomposers, which break down the dead organisms and return their nutrients to the soil/environment • Trophic Interactions o Trophic cascade: the effects on one level influence the other levels § Top-‐down effect: when the effects flow down through a trophic chain (issue with tertiary consumer affects primary producers) • Ex. introducing a new predator § Bottom-‐down effect: when the effects flow up through a trophic chain (issue with primary producers affects tertiary consumers) • Ex. more primary producers 4-‐22-‐16 Species Richness (Biodiversity) and Stability • Biodiversity is influenced by: o Primary productivity (sunlight and primary producers) o Habitat heterogeneity (the more organisms are able to live in a habitat, the more diversity in species) § Habitat heterogeneity is the ability of a habitat to accommodate more species o Climatic factors § More species might be expected to coexist in a seasonal environment • Species rich/biodiverse ecosystems do better at resisting compositional changes in habitat • Diversity stability hypothesis: preexisting stability between species in an environment causes difficulty for foreign species to move in because there is already a very stable biomass (number of organisms in balance) o More species in a habitat causes less year-‐to-‐year variation in biomass o If there is a drought, the resulting biomass decrease is negatively related to species richness Ecosystem Dynamics: An Example • Primary Producers (can only be photosynthetic organisms) o Grass • Primary Consumers o Bison o Grasshoppers • Secondary Consumers o Squirrels o Cattle Egrets o Prairie Dogs • Tertiary Consumers o Owls • Herbivory: Grasshoppers (+)/Grass (-‐) ; Bison (+)/Grass(-‐) • Commensalism: Cattle Egrets (+)/Cattle (0) • Competition: Bison (-‐)/Grasshopper (-‐) ; Squirrels (-‐)/Prairie Dogs (-‐) • Food Web: Owl Tertiary Consumers Prairie Dog Squirrel Cattle Egret Secondary Consumers Grasshopper Bison Primary Consumers Grass Primary Producers Decomposers Nutrients in soil A set of arrows points from all organisms to these 2 things; all other arrows point from each organism to the next row up Biomes: Climate and Habitat are Viewed as the Same Thing • Seasons are due to a tilt in earth’s axis; the equator is always hotter because of concentrated sunrays • Earth’s air circulates; the equator has warm air, and as warm air rises, it dumps its water (causing rainforests) o Every 30 degrees of latitude (up and down), water goes back into the atmosphere (deserts are found around these areas) • The Rain Shadow Effect: o Winds have to rise over mountains, and as they rise they cool, which causes them to dump rain wherever the air starts to get cooler (the side of the mountain away from the wind is dry, while the side by the wind is rainy) o The rain shadow itself is the dry side of the mountain • Evapo-‐Transpiration Ratio o This is the ratio of evaporation to transpiration o Deserts: low precipitation, rapid evaporation; plants reduce transpiration (high rate) o Rainforests: high precipitation, high evaporation and transpiration (low ratio) • Terrestrial Biomes reflect the distribution of climate and topography o Elevation and latitude determine rainfall • Terrestrial Biomes: o Desert: little rain and resources o Tropical Rainforest: high temperature, precipitation, and diversity o Savanna: tropical grasslands with seasonal rain o Chaparral: shrubs, small trees, adapted to withstand fire o Temperate Grassland: rich soil between equator and poles o Temperate Deciduous Forests: mild seasonal climate, plentiful rains o Temperate Coniferous Forests: along coastlines in temperature climates o Taiga: northern forest where winters are harsh o Alpine: similar to tundra, but no permafrost below soil o Tundra: mostly frozen, treeless, short growing season, permafrost Temperature and Precipitation Determine Biomes and Primary Productivity Levels o Productivity and precipitation as well as productivity and temperature are both generally directly related o Tropical rainforests, therefore, have the highest productivity o There is way more water on earth than land o Aquatic Biomes: o Freshwater: lakes and ponds, rivers and streams o Saltwater: open ocean, estuaries and wetlands o Photic zone in open ocean is only zone that can contribute to primary productivity (upper 200 m) Review Questions 1. Resource partitioning in Anolis lizards is an example of a. Intraspecific competition b. Interspecific competition c. Interference d. Exploitative competition 2. Resource partitioning reults in: a. Individuals of each species sharing resources they both use b. Individuals of each species hybridizing in regions of overlap c. Movement from fundamental niche to realized niche for both species d. Movement from realized niche to fundamental niche for both species 3. Which best describes the kind of resources individuals compete for? a. Food/nutrients b. Space/shelter c. Mate access d. Can be any resource that is limited in an environment 4. Cows have bacteria in their rumen that can digest cellulose. What is the relationship between the cow and the bacteria? a. Parasitism b. Commensalism c. Predation d. Mutualism e. Antagonism 5. When humans are born their guts are first colonized by bacteria that are able to live independently; but eventually these bacteria are replaced by bacterial species that can only survive inside the human gut. Which of the following is true? a. This is a commensalistic relationship that begins with facultative species and ends with obligate species b. This is a parasitic relationship that begins with obligate species and ends with facultative species. c. This is a mutualistic relationship that begins with facultative species and ends with obligate species. d. This is an antagonistic relationship that begins with facultative species and ends with obligate species. 6. The volcanic oceanic island of Krakatoa is located in Indonesia. In 1883, this island experienced a massive volcanic explosion that killed most of the plants and animals living on the island. After a very, very long time period of recovery from the eruption, which group of organisms would we expect to have the most representation among native species on the island? a. Lizards b. Small mammals c. Birds d. Beetles 7. In this food web, which of the following describes the minnow fry? a. Primary producer b. Primary consumer c. Secondary consumer d. Tertiary consumer 8. In general, a larger biomass in primary producers for a trophic pyramid: a. can support more biomass at higher trophic levels because more energy is available between the level of primary producer and primary consumer. b. does not affect the amount of biomass that can be supported at the level of primary producer. c. can support less biomass at higher levels because more energy is lost between the level of primary producer and primary consumer. 9. Which one of the following statements about the trophic cascade in the sea otter and sea urchin-‐kelp communities along the West Coast of North America is FALSE? a. Increased sea otter populations are linked to reduced sea urchin populations b. Increased orca (killer whale) predation on sea otters is linked to more profuse growth of kelp forest. c. Increased sea otter populations are linked to more profuse growth of kelp forests. d. Increased orca (killer whale) predation on sea otters is linked to increased sea urchin populations. 10. Pertaining to the example food web: In a drought year, there is much less grass biomass produced. What would you expect to happen to the number of owls? a. Increase b. Decrease c. Stay the same 11.Pertaining to the example food web: In a drought year, there is much less grass biomass produced, leading to a decrease in the number of owls. This is an example of: a. Top-‐down effect b. Bottom-‐up effect c. Diversity stability hypothesis Answers: 1. B. interspecific competition 2. C. movement from the fundamental niche to the realized niche for both species 3. D. can be any resource limited in an environment 4. D. mutualism 5. C. mutualistic, facultativeàobligative 6. D. beetles 7. C. secondary consumer 8. A. more biomass at higher temperatures 9. B 10.B. decrease 11.B. bottom-‐up effect