Bio U3 detailed

Genetic diversity vs species diversity vs ecosystem diversity

genetic diversity = variation in genes within a species; species diversity = number + abundance of species; ecosystem diversity = variety of ecosystems in an area

Biological species concept

organisms that can interbreed and produce fertile offspring

Limitation of biological species concept

doesn’t apply to asexual organisms or extinct species; ignores hybrids

Linnaean classification system

hierarchical system: Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species

Purpose of taxonomy

to organise, name and show relationships between organisms

Binomial nomenclature

two-part scientific naming system: Genus species (e.g. Homo sapiens)

How dichotomous keys work

step-by-step choices based on traits to identify organisms

Lincoln Index formula

N = (M × n) / m (estimate population size)

Lincoln Index variables

N = estimated population, M = marked, n = total caught second sample, m = recaptured marked

Species richness

number of different species in an area

Species evenness

distribution of individuals among species

Simpson’s Diversity Index formula

SDI = 1 − [Σ n(n−1) / N(N−1)]

Meaning of high SDI

value closer to 1 = high biodiversity

Random sampling

each location has equal chance of selection

Systematic sampling

samples taken at regular intervals

Stratified sampling

ecosystem divided into strata then sampled proportionally

Quadrat sampling

used for plants/slow organisms in fixed area squares

Line transect

samples taken along a line to show change in distribution

Belt transect

wider version of line transect using quadrats in a strip

Capture-recapture method

used for mobile populations to estimate size

Reducing sampling bias

increase sample size, random numbers, consistent criteria, calibrated tools

Abiotic factors

non-living factors like water, light, temperature, nutrients

Biotic factors

living interactions like predation, competition, disease

Species distribution patterns

clumped, random, uniform

Why microhabitats matter

create small environmental differences affecting species presence

Exponential growth (J-curve)

population grows rapidly with unlimited resources

Logistic growth (S-curve)

growth slows as resources become limited, reaches carrying capacity

K-selected species

low reproduction, high survival, stable populations

r-selected species

high reproduction, low survival, rapid population growth

Population growth rate formula

(births + immigration) − (deaths + emigration)

Specht classification system

classifies ecosystems based on dominant vegetation structure

Holdridge life zones

classification using temperature, rainfall, and humidity

Energy conversion in ecosystems

light energy → chemical energy via photosynthesis

Biomass

organic material stored in organisms

Carbon cycle

role of organisms in cycling carbon through photosynthesis and respiration

Energy loss in ecosystems

most energy lost as heat during respiration

Food chain

shows linear energy flow from producer to consumers

Food web

interconnected food chains in an ecosystem

Ecological pyramid

shows energy, biomass or numbers at trophic levels

Energy transfer efficiency

only ~10% transferred between trophic levels

Gross productivity

total energy produced by producers

Net productivity

energy stored after respiration losses

Water cycle movement

evaporation → condensation → precipitation → runoff

Nitrogen cycle

role of bacteria in nitrogen fixation, nitrification, denitrification

Predation

one organism kills and eats another

Competition

organisms compete for limited resources

Mutualism

both species benefit

Commensalism

one benefits, other unaffected

Parasitism

one benefits, host harmed

Ecological niche

role and position of a species in ecosystem

Competitive exclusion principle

two species cannot occupy identical niches long-term

Keystone species

species with large impact on ecosystem despite small numbers

Effect of removing keystone species

ecosystem structure can collapse or change drastically

Overexploitation

overuse of species leading to population decline

Habitat destruction

removal of natural environment reduces biodiversity

Monoculture

growing one crop reduces biodiversity and resilience

Pollution

harms organisms and disrupts ecosystems

Carrying capacity

maximum population ecosystem can sustain

Factors affecting carrying capacity

resource availability, climate, disease, predators

Primary succession

life starts from bare rock/no soil

Secondary succession

recovery after disturbance where soil remains

Pioneer species

first species to colonise harsh environments

Features of pioneer species

hardy, fast-growing, tolerate extreme conditions

Succession changes over time

increase in biodiversity, biomass, and soil quality

Climax community

stable final stage of succession

Ecological data interpretation

use food webs/data to predict ecosystem changes

First Nations ecological knowledge

long-term observation of ecosystems used for land management and biodiversity understanding

Keystone species conservation debate

focus on single species may ignore full ecosystem complexity

Fossil record evidence

shows past ecosystems and evolutionary changes

Sedimentary rocks

preserve evidence of ancient organisms and environments