IB Biology HL - Ecology and defense against disease

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ecosystem stability

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149 Terms

1

ecosystem stability

ability of an ecosystem to maintain it’s structure + function over long periods of time (despite disturbances)

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ecological structure

physical + geological structures of the landscape, biodiversity, population size, interactions in the community

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ecological function

processes (e.g. water cycling)

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requirements for stability

  • constant energy supply (energy lost at each trophic level) - main source is sunlight

  • nutrient cycling (logging removes nutrients)

  • high genetic diversity - enables populations to adapt to changes in the environment by natural selection

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tipping point

shift in ecosystem leading to a new equilibrium state

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how deforestation can lead to a new equilibrium state

causes a reduction in evapotranspiration and rainfall which could lead to a tipping point where the rainforest cant recover and becomes a savannah

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keystone species

species whose activity has a disproportionate effect on the structure of an ecological community - help to maintain biodiversity in an ecosystem

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sustainability

  • use and management of resources allowing full natural replacement of the resources is exploited and full recovery of ecosystems is affected by the attraction and use

  • if the harvest is equal to (or less) than the growth in population, sustainable use of the resources is possible

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max sustainable yield

amount that is removable without depleting the original stock or affecting its’ ability to recover

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issues with intensive large scale farming

  • soil erosion

  • leaching

  • fertiliser

  • agrochemicals

  • carbon footprint

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soil erosion

  • cause = tillage of soil (prep for crop), lack of crops (no roots to hold soil), wind + water

  • solution = use cover crops (during winter, etc) to hold soil

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leaching

  • removal of nutrients from soil by percolation of water

  • cause = removal of plants

  • solution = improve irrigation or use cover crops

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fetiliser

  • used to replace nutrients

  • cause = doesn’t improve soil structure, is energy intensive, can lead to eutrophication

  • solution = reduce leaching, use appropriate amount of fertiliser at right time, use green fertiliser

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agrochemicals

  • artificial fertiliser

  • cause = monocultures encourage pest/weed problems = increase in the use of pest/herbicides

  • solution = use organic manure, crop rotations, mixed cropping, biological pest controls

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carbon footprint

  • cause = clearing land, machinery (fossil fuels), etc

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eutrophication

  • enrichment of water with nutrients which stimulates excessive algae growth (e.g. nitrogen and phosphorous)

  • the decay of dead algae leads to low oxygen conditions and damage to ecosystems

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causes of eutrophication

  • agricultural fertiliser

    • have high nitrogen/phosphorous contents

    • leaching - excess fertiliser gets washed out of soil by rain and goes into ponds/rivers)

    • rivers bring nutrients to oceans

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process of eutrophication

  • increase in concentration of nitrogen/phosphorous in water leads to algae blooming

  • the algae dies and sinks to the bottom of the lake/pond

    • accumulation of dead organic matter

    • increases the activity of decomposers

  • increased use of oxygen in water by the decomposers for cell respiration increases the biological oxygen demand

  • leads to a decrease in dissolved oxygen levels in the water

    • kills fish, shells, other organisms

  • decrease in light at bottom of lake/pond (dead organic matter build up) = organisms can’t photosynthesise and die

  • decomposition of dead organisms = release of phosphates and nitrates into water

  • = positive feedback loop

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biological oxygen demand (BOD)

measure of the amount of oxygen required to breakdown organic material (aerobic respiration of microorganisms)

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why BOD can increase

more organic waste in water leads to more organisms using waste for cell respiration which leads to an increase in demand for oxygen

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impact of eutrophication

cyanobacteria produce toxins that make people sick/die

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bioaccumulation

build up of non-biodegradable/slow biodegrading chemicals in body

  • many toxins are not biodegradable

  • organisms store the toxins in their fat

  • over time the concentration of toxins absorbed increases

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biomagnification

process whereby concentration of chemicals increases at each trophic level

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pollution by DDT

  • DDT = effective insecticide (very hydrophobic)

    • is strongly absorbed by soils (half-life average of 15 years)

    • not soluble in water

  • uses = WWII control of malaria mosquitoes, control typhus lice, agriculture rids of insects and increases yield

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case study DDT

  • DDT biomagnification = thinning of bird egg shells

    • eggs crushed during incubation = less chicks hatched = decrease in population

    • threatened survival of species

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macroplastics

  • larger than 5mm

  • majority washed into oceans by rivers

  • ocean current accumulates plastic into large patches

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microplastic

  • smaller than 5mm diameter

  • degrades leaving toxins in ocean

  • carbon compounds accumulate on/in plastic with toxic effects when ingested

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rewilding

conservation method

  • allows natural processes in ecosystem to recover

    • as little human intervention as possible

  • some intervention is needed

    • control of invasive species - reintroduce apex predators, distribute seeds, introduce keystone species

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rewilding case study

Hinewai reserce

  • removed alien species (goats, possum, deer)

  • nurse plants from alien plants

    • allows native species to re-establish themselves = protection younger seeds

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succession

orderly process of change over time in ecosystem

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primary succession

starts with formation of soil (volcano, glacier recedes, etc)

  • soil formed by weathering of rock + decay of dead plants and animals

  • takes 100s of years

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secondary succession

  • formation of an eco-system with soil present (e.g. after a fire a beaver builds a dam)

  • os a faster process

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stages of primary succession

Stages of Primary Succession

  1. Bare Rock: The process begins on bare rock after a disturbance (e.g., volcanic eruption).

  2. Pioneer Species: Lichens and mosses colonize the area, breaking down rock into soil.

  3. Soil Formation: As pioneer species die, they contribute organic matter, enriching the soil.

  4. Intermediate Species: Grasses and small plants grow, further improving soil quality.

  5. Shrubs and Young Trees: Larger plants establish, leading to increased biodiversity.

  6. Climax Community: A stable ecosystem forms, often dominated by mature trees, representing the final stage.

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arrested succession

community not reaching its expected climate community due to human interference

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main gases in climate change

  • carbon dioxide

  • methane

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the greenhouse effect

  • long wave radiation - absorbed by greenhouse gas molecules in atmosphere (warms them up)

  • greenhouse gas molecules emit heat as long wave radiation

  • earths surface warms up - emits more long wave radiation

  • = warming up of earths surface and lower atmosphere due to presence of greenhouse gases

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enhanced greenhouse gas

increased greenhouse effect due to human activities increasing the concentration of greenhouse gases = climate change

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climate

a regions general pattern of weather conditions over a long period of time

  • determined by the average insolation, precipitation, temperature

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weather

short term atmospheric condition

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ice core drilling

gas trapped in fossilised ice analysed to determine carbon dioxide concentration

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proxy measurement

determining temperature using ratio of carbon dioxide isotopes present in air

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albedo

proportion of solar radiation reflected by a particular body or surface

  • high albedo = clouds, ice, snow

  • low albedo = water

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reduced albedo effect

warm temps =

  • snow + ice melt

    • reduced albedo

      • more absorption solar energy

        • warmer temp

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permafrost

ground that is frozen all year - frozen soil locks lots of carbon dioxide

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oceans as a carbon dioxide sink

more co2 diffuses into ocean than out (locked by photosynthesis and phytoplankton)

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oceans as a carbon dioxide source

atmospheric temperatures increase lead to ocean temps increasing

  • warm water holds less co2 = released into atmosphere

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thawing of permafrost

  • temp increases

    • ground thaws

      • detritus decomposes

        • increases release of co2 and methane

  • temp increase

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forest browning

lack of water = reduced photosynthesis

  • lower primary productivity

    • less co2 removed from atmosphere

    • pine needles lose chlorophyll = forest browning

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how ocean currents effect the climate

ocean currents - mainly caused by changes in water density due to temp + sailinity

currents distribute heat around globe effecting the climate

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nutrient upwelling

  • deep ocean current forced upwards when they reach a continental shel

  • brings nutrient rich water to the surface where light can penetrate

  • carbon fixed by photosynthesis =

    • high primary productivity

    • energy enters marine food chains

  • dead organisms sink to bottom + decompose

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upslope range shift

montane species live at specific elevations on the mountain

  • an increase in altitude leads to an average temperature decrease

    • climate change increases temp = species move up mountain

  • leads to interspecific competition

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ocean warming

as atmospheric temp increases, ocean temp increases

  • co2 concentration in atmosphere leads to more diffusing into ocean

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coral bleaching

  • zooxanthellae live inside reef coral tissue (mutualistic relationship)

  • when coral is under stress it expels the algae which leads to bleaching, starvation, and death

    • stress triggers = low light (sedimentation), temp increases (kills algae), and ocean acidification (low pH)

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relationship between coral and zooxanthellae

algae

  • photosynthetic = gives coral glucose, amino acids, oxygen

coral

  • gives protection so algae can be closer to surface of water with more light

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ocean acidificaion

increased co2 in atmosphere leads to more diffusing into ocean

  • co2 reacts with h20 to make carbonic acid

  • carbonic acid turns into hydrogen and hydrogen carbonate ions

    • makes pH of water more acidic

  • increase H+ ions react with CO3(2-)

    • balances the shift and less available for organisms to build skeletons/shells

  • increase drop in pH = exisiting shells and skeletons dissolve

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afforestation

planting trees where they don’t already grow

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peat wetlands

  • largest terrestrial carbon sink

  • develop naturally in temperate + boreal ecosystems + tropical

  • drained and excavated for fuel, fertiliser, and oil

  • restore them to save the carbon sink function

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phenology

study of periodical events synchronized with seasons

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photoperiod

number of hours sun is shining and the change in temperature

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spruce bark beetles case study

climate changes leads to weaker trees and more beetles

  • the beetles attack the trees

    • trees no longer survive due to being weaker and more beetles attacking

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habitat

environment in which a species, population, or organism normally lives

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geographical location

specific area/region where a species lives

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physical location

immediate environment where species lives

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adaptations

organisms features aiding in survival by being better suited for the environment

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adaptations to grass in sand dunes

rolled leaves = stomata in rolled leaves release less water

stomata in pits = traps water vapour decreasing transpiration

waxy cuticle = reduce water loss

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adaptations to trees in mangroves

salt excretion = some parts of plant have salt glands to eliminate salt

tissue partitioning = concentrate soil in designated leaves then drop them (abscission)

pneumatophores = tubes allowing oxygen to reach roots

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abiotic features

non-living factors affecting eco-system

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examples of abiotic features

  • water

  • light

  • soil

  • temperature

  • minerals

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biomes

geographical areas with a particular climate and sustain a specific community of flora and fauna

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tropical rainforest

  • hot climate (25-30)

  • high levels of precipitation

  • large diversity in species + vegetation

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temperate forest

  • moderate temps

  • clear seasonal changes

  • growing period (200 days) during 4-6 frost free months

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taiga

  • cold + icy

  • small amount precipitation

  • coniferous trees densely packed

  • little variation in species

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grassland

  • moderate temps

  • moderate amount of rainfall

  • tress/shrubs largely absent

  • grass is dominant vegetation

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tundra

  • freezing temos

  • very little precipitation

  • vegetation is low growing

  • perennial plants during summer

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hot desert

  • extreme temp conditions

  • low precipitation

  • dominant plants species is xenophytes (water conservation)

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convergent evolution

different evolutionary lineages developed similar mechanisms due to similar ecological niches

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fennec fox adaptations for hot desert

water conservation = kidneys adapted to restrict water loss

temp regulations = dissipates efficiently due to large ears keeping a cool body temo

burrowing = digs extensive burrows making a colder environment to raise young

paws = thick fur to protect from hot sand and aid in digging

nocturnal = avoid extreme heat in day

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saguaro cactus case study

photosynthesis = has a special adaptation allowing it to take in co2 at night and store for the next day = minimal water loss

water storage = absorbs and stores large amounts of water to use during drought periods

thick waxy cuticle = reduces water loss through evaporation

spines = modified leaves reducing water loss, providing shade, and protection from herbivores

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brown throated sloth adaptations for tropical rainforest

long limbs + strong claws = good for hanging and climbing

slow metabolism = adapted for low energy diet (leaves), slow pace consumes energy when habitat food is nutrient poor + hard to digest

infrequent ground visits = reduces risk of predation

camouflaging fur = can host algae to blend into greenery and hide from predators

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scarlet star (flower) adaptations for tropical rainforest

water collection and storage = leaves from central tank storing water. crucial when roots are used for anchorage not water absorption.

brightly coloured bracts = surround small flowers to attract pollinators in dense rainforest

epithytic growth = grows on other plants without parasitising them. allows better light conditions above the forest floor and reduced competition for soil nutrients.

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ecological niche

specific role played by a species in its habitat

  • includes food, where it lives, etc

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biotic factor

living things within an ecosystem

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examples of biotic factors

  • plants

  • bacteria

  • animals

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aerobic

processes or activites requiring presence of oxygen

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obligate anaerobes

respire anaerobically and can only survive in absence of oxygen

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facultative anaerobes

can respire anaerobically or aerobically depending on oxygen availability

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obligate aerobes

resire aerobically and cannot survive in absense of oxygen

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autotroph

organisms that can produce their own energy

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heterotroph

organisms that cannot produce their own energy

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mode of nutrition

method by which an organisms obtains its energy and nutrients

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holozoic nutrition

when organisms ingest a variety of organic material, which then undergoes a series of metabolic processes such as internal digestion, absorption, and assimiliation

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assimilation

occurs when absorbed products are delivered to specific cells that will use them

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mixotrophic nutrition

use both autotrophic and heterotrophic forms of nutrition (mainly occurs in unicellular organisms)

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protist

any eukaryotic organism that is not an animal, land plant, or fungus

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obligate mixotrophs

obligated to use both auto/heterotrophic means of nutrition to survive.

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facultative mixotrophs

can switch between auto/heterotrophic nutrition, but do not depend on any for its survival.

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decomposer

organism that breaks down and recycles dead or decaying organic matter

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saprotrophs

decomposers releasing digestive enzymes then absorb the external products of digestion

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extremophiles

live in extreme hot/cold, salinity, other conditions that are hostile to most other forms of life on earth

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photoautotrophs

do a form of photosynthesis using pigments other than chlorophyll and do not generate oxygen

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