IB Biology HL - Ecology and defense against disease

ecosystem stability

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

ecological structure

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

ecological function

processes (e.g. water cycling)

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

tipping point

shift in ecosystem leading to a new equilibrium state

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

keystone species

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

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

max sustainable yield

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

issues with intensive large scale farming

• soil erosion

• leaching

• fertiliser

• agrochemicals

• carbon footprint

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

leaching

• removal of nutrients from soil by percolation of water

• cause = removal of plants

• solution = improve irrigation or use cover crops

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

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

carbon footprint

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

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

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

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

biological oxygen demand (BOD)

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

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

impact of eutrophication

cyanobacteria produce toxins that make people sick/die

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

biomagnification

process whereby concentration of chemicals increases at each trophic level

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

case study DDT

• DDT biomagnification = thinning of bird egg shells

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

  • threatened survival of species

macroplastics

• larger than 5mm

• majority washed into oceans by rivers

• ocean current accumulates plastic into large patches

microplastic

• smaller than 5mm diameter

• degrades leaving toxins in ocean

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

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

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

succession

orderly process of change over time in ecosystem

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

secondary succession

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

• os a faster process

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.

arrested succession

community not reaching its expected climate community due to human interference

main gases in climate change

• carbon dioxide

• methane

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

enhanced greenhouse gas

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

climate

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

• determined by the average insolation, precipitation, temperature

weather

short term atmospheric condition

ice core drilling

gas trapped in fossilised ice analysed to determine carbon dioxide concentration

proxy measurement

determining temperature using ratio of carbon dioxide isotopes present in air

albedo

proportion of solar radiation reflected by a particular body or surface

• high albedo = clouds, ice, snow

• low albedo = water

reduced albedo effect

warm temps =

• snow + ice melt

  • reduced albedo

    • more absorption solar energy

      • warmer temp

permafrost

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

oceans as a carbon dioxide sink

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

oceans as a carbon dioxide source

atmospheric temperatures increase lead to ocean temps increasing

• warm water holds less co2 = released into atmosphere

thawing of permafrost

• temp increases

  • ground thaws

    • detritus decomposes

      • increases release of co2 and methane

• temp increase

forest browning

lack of water = reduced photosynthesis

• lower primary productivity

  • less co2 removed from atmosphere

  • pine needles lose chlorophyll = forest browning

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

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

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

ocean warming

as atmospheric temp increases, ocean temp increases

• co2 concentration in atmosphere leads to more diffusing into ocean

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)

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

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

afforestation

planting trees where they don’t already grow

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

phenology

study of periodical events synchronized with seasons

photoperiod

number of hours sun is shining and the change in temperature

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

habitat

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

geographical location

specific area/region where a species lives

physical location

immediate environment where species lives

adaptations

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

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

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

abiotic features

non-living factors affecting eco-system

examples of abiotic features

• water

• light

• soil

• temperature

• minerals

biomes

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

tropical rainforest

• hot climate (25-30)

• high levels of precipitation

• large diversity in species + vegetation

temperate forest

• moderate temps

• clear seasonal changes

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

taiga

• cold + icy

• small amount precipitation

• coniferous trees densely packed

• little variation in species

grassland

• moderate temps

• moderate amount of rainfall

• tress/shrubs largely absent

• grass is dominant vegetation

tundra

• freezing temos

• very little precipitation

• vegetation is low growing

• perennial plants during summer

hot desert

• extreme temp conditions

• low precipitation

• dominant plants species is xenophytes (water conservation)

convergent evolution

different evolutionary lineages developed similar mechanisms due to similar ecological niches

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

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

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

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.

ecological niche

specific role played by a species in its habitat

• includes food, where it lives, etc

biotic factor

living things within an ecosystem

examples of biotic factors

• plants

• bacteria

• animals

aerobic

processes or activites requiring presence of oxygen

obligate anaerobes

respire anaerobically and can only survive in absence of oxygen

facultative anaerobes

can respire anaerobically or aerobically depending on oxygen availability

obligate aerobes

resire aerobically and cannot survive in absense of oxygen

autotroph

organisms that can produce their own energy

heterotroph

organisms that cannot produce their own energy

mode of nutrition

method by which an organisms obtains its energy and nutrients

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

assimilation

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

mixotrophic nutrition

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

protist

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

obligate mixotrophs

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

facultative mixotrophs

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

decomposer

organism that breaks down and recycles dead or decaying organic matter

saprotrophs

decomposers releasing digestive enzymes then absorb the external products of digestion

extremophiles

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

photoautotrophs

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