Lecture Notes on Population and Community Ecology PDF

→ LECTURE 18: Population ecology(study of interactions determining distribution and abundance) Population: - group of individuals from same specie living in the same area and time and breed with one another - Described by the boundaries and size Metapopulation - Group of geometrica...

→ LECTURE 18: Population ecology(study of interactions determining distribution and abundance) Population: - group of individuals from same specie living in the same area and time and breed with one another - Described by the boundaries and size Metapopulation - Group of geometrically separated populations of same species and interact at some level Density : number of individuals within a population per area results from immigration and emigration Species range: area where a certain species can be found Dispersion: - spacing between individuals within the boundaries of population Patterns: 1.Clumped spacing→ uneven distribution of resources, group together 2. Uniform spacing → behavioural interaction/resource competition, evenly distributed 3. Random spacing→ don't interact strongly with one another, independent of others Types of interactions Abiotic Biotic How organisms react with non-living How organisms react with other components organisms If other species do not set limits on Negative effects of predators, diseases actual range, we are left with the Positive effects of food sources possibility that some physical or chemical factors set the range limits. Like water availability and temperature Immigration: - New individuals from other areas Emigration: - Movement of individuals out of a population To determine a population size: 1. Sampling: counting the number, with constant density 2. Mark-Recapture: for mobile populations. 1. Capture random sample S 2. Mark and release them 3. Wait for them to mix in the population 4. Capture a second sample 5. Count number of marked sample X and the total number of animals captured n N= sn/X S is the marked and released animals from first round X is captured and marked animals in second capture n total number of animals capture in the second round N number of population → population grow by: 1. Birth > death 2. Immigration > emigration Change in population size = birth - deaths Population dynamics → Exponential population growth: - Population where all individuals have access to abundant food and reproduce Per capita rate of increase: dN/dt= ri N dN being change in population size dT change in time Ri the intrinsic rate of natural increase for the population N is the number of individuals in the population - Population that grow exponentially, with a constant rate, assuming unlimited resources → Logistic population growth: - Change in growth rates as population size is close to K Per capita rate of increase: approaches 0 Carrying capacity: (K) - Maximum population size that a certain environment can sustain - Varies over space and time Population grows within its habitat=Population density increase Density dependent is a process influenced by a population density: - Limiting resources, predation, emigration, disease that spread more rapidly at high density Density independent is a process NOT influenced by a population density - weather , earthquakes, severe cold Demography: - Study of statics of population and how they change over time Life table: - survival pattern of a population depending on age Cohort: - Group of individual of same age Survivorship curves: - Graphic method of data in a life - Type 1: low death rates - Type 2: constant death rate - Type 3: high death rate → LECTURE 21: ECOSYSTEMS ECOLOGY( study about the living and nonliving components in the environment ) - Ecosystem: all organisms living in a community 1. Energy flow through an ecosystem: energy transfer is never 100% efficient Ex. sunlight enters as light and exists as heat Ex. decomposition Primary producers → plant Herbivores → primary consumers ( ants) Herbivores do not digest everything they eat, some are excreted as feces Detritivores → bacteria and fungi → primary production: - Amount of light energy converted to chemical energy by autotrophs GROSS PRIMARY PRODUCTION: total PP in an ecosystem NET PRIMARY PRODUCTION: GPP- the glucose used by primary producers for cellular respiration NPP= GPP-Ra → secondary production: - Amount of energy in consumers food that is converted to their OWN new biomass PRODUCTION EFFICIENCY: - Fraction of energy stored in food that is used for secondary production PE= net secondary production / assimilation of primary production x 100% NSP is the energy stored in biomass represented by growth and reproduction Assimilation is the total energy taken in that is used for growth  2. Nutrient Cycling through an ecosystem: - Cycle between the biotic and abiotic part of an ecosystem - An example would be water, carbon, nitrogen Carbon cycle: forms the framework of the organic molecules that are essential to life Ex. Photosynthetic organisms convert CO2 to organic molecules used by heterotrophs. 3. Anthropocene global environmental change - Pollution: Excess nutrients like fertilisers that stay in soil until rain and run off into water Ex. Eutrophication→ excess nutrients in the water body that causes pollution in water and leads to algal bloom. Dead plants are broken down into bacteria which use more O2. The oxygen level increases and aquatic life dies - Chemical pollution: Human release toxic chemicals in environment Ex. Biological magnification→ concentrates toxin at higher trophic levels, where biomass is lower → LECTURE 21: CLIMATE CHANGE Weathers: short term atmospheric condition ( given day ) climate: long term atmospheric condition Climate change: significant lasting change in the statistical distribution of weather Ex. increased temperature, loss of sea ice, increased sea level 1. Temperature will rise further 2. Precipitation will become more extreme 3. 1˚C global temperature rise à 7% rise in moisture content 4. Global mean sea level is rising Higher global temperature→ more evaporation→ more water vapor in the atmosphere → higher moisture content Anthropogenic climate change: change in climate related to GREENHOUSE GAS production emitted by human activity. Emission from human activity → Ex causes of climate change: 1. greenhouse gas effect that absorbs and emits radiation H2O (water vapor) CO2 CH4 (methane) that help absorb energy and heat from sun 2. CO2 emission by human activities like industry, electricity and transportation → Impacts: 1. Change in species distribution 2. Extinction: The Amazon could lose 69% of its plant species. 3. Species range shift, species relocating to other areas with more tolerable climate 4. Phenological shift: changes in the timing of life history events relative to calendar dates → How to reduce it: 1. Increase energy efficiency 2. Low carbon electricity 3. Decarbonised fuels ( biofuels) →LECTURE 19: COMMUNITY ECOLOGY ( different species that live and interact in the same place and time) Ecological niche: - Total of organisms use of the biotic and abiotic resources INTERSPECIFIC INTERACTIONS: 1. Competition (-/-): - different species compete for different resources in short supply - Overlap of niches - Competitive exclusion: elimination of one of the competing species - Resource partitioning: Individuals of a species can adjust what or when they eat and where they live to minimize competition. - Character displacement: the species adapt to new resources leading to accumulation of adaptive traits 2. Predation (+/-): - Predator kills and eats the prey - Predator feeding adaptations: teeth, claws, poison - Strategy: camouflage to avoid being noticed - Prey defensive adaptation: camouflage, running - Strategy: hiding and living in groups also mimicry COLOURATION Aposematic Cryptic Batesian mimicry Mullerian mimicry Warning colors that Camouflage Harmless species Species that predators avoid Harder to see mimics a harmful resemble each other Bright colours= one chemical defenses - Natural selection shapes the body forms and behaviors of both predators and prey 3. Herbivore (+/-): - Herbivore eats parts of a plant - led to the evolution of plant mechanical (spines, tough leaves) and chemical defenses and consequent adaptations by herbivores 4. Parasitism (+/-): - Parasite derives its nourishment from an organism that is harmed in the process 5. Mutualism (+/+): - Both species are benefiting (ex. Bacteria in the human intestine) 6. Commensalism (+/0): - One specie is benefiting while the other isn’t affected → Species diversity: - Biological community includes species that influence each other through interactions - The nature of the interactions within a community depends on its species composition:Number of species present, their relative abundances and their feeding relationships (trophic rank). - Biodiversity is measured by: 1. Species richness → number of species present in a community 2. Relative abundance→ proportion of each species To measure diversity: High diversity index (H) indicates more diverse community Shannon diversity index H = – (pA ln pA + pB ln pB + pC ln pC + …) A, B, C... are the species p is the relative abundance of each species ln is the natural logarithm →Productivity: refers to the rate of generation of biomass (primary and secondary production) in an ecosystem. →Stability: refers to the temporal constancy of a community, resistance to environmental change, or resilience after a disturbance. → dominant species: are most abundant have the most biomass → keystone species: not the most abundant but have important ecological roles → Food chains: - Transfer of food energy up the trophic level. → Food webs: trophic interactions within a community and are composed of multiple food chains and give a better understanding of how species interact with each other  - Bottom-up control: influence from lower to higher trophic levels - Top-down control: predation controls community because predators limit herbivores, which limits plants and nutrients → Trophic cascade: Increase in primary producers (plants / phytoplankton) due to impact of predators on herbivores. Disturbance: - storm, fire, flood, drought that changes a community by removing organisms or altering resource availability - How communities are affected by disturbances will depend on the types of disturbances and their frequency and severity. - High level= high intensity and frequency disturbance - Low level= low intensity and frequency Ecological succession: is the transition in species composition in disturbed areas 1. Primary succession: lifeless area 2. Secondary succession: existing community has been removed by a disturbance 3. Stable final stage is the climax community