QCE Biology Units 3 + 4

Biodiversity

the total variety of organisms, habitats, communities and ecological processes in the biosphere

High biodiversity

the ecosystem is healthy and more likely to withstand sudden changes

Low biodiversity

the ecosystem is susceptible to small change and likely to collapse

3 factors making up biodiversity

genetic, species, ecosystem

Species richness

number of different species represented (count of species)

Species richness index

D = S/√N (no. species / √no. individuals)

Evenness (relative abundance)

a description of the number of individuals of a species in relation to the total number of individuals in an area

Percentage cover

proportion of an area covered by an organism (i.e.: estimating plant frequencies)

Advantages of percentage cover

good estimate of abundance, more efficient than counting individuals

Disadvantages of percentage cover

plants in flower overestimated, low-growing plants underestimated, poor quadrat sampling means some rare species can be missed

Emergent layer

tallest / most predominant layer, produces the most above-ground biomass

Percentage frequency

appearance of plant species in sample quadrats
% freq = [no. quadrats containing species]/[total no. quadrats]

Simpsons Diversity Index

measure of diversity that takes into account the number of species and relative abundance
D = 1 - ([Σn(n-1)]/[ΣN(N-1)])

Intraspecific interactions

interactions between the same species

Interspecific interactions

interactions between different species

Predation

predator kills prey for food

Competition

organisms competing with one another for limited resources (food, space, mates)

Symbiosis

2 different species living together in direct contact (3 forms)

Mutualism (symb.)

both species benefit (++)

Commensalism (symb.)

one species benefits, other unaffected (+0)

Parasitism (symb.)

one species benefits, other harmed (+-)

Disease

any condition that impairs the normal activity of an organism (infectious & non-infectious)

Abiotic factors (examples)

Climate - rainfall, temperature, wind, sunlight
Substrate
Soil - structure, porosity, pH, salinity
Size / Depth of area

Biotic factors (examples)

Types of plants & animals
Inter/intraspecific species interactions

Spatial scale

space, geographical location... spatial patterns of distribution

Temporal scale

time... change occurring over a period of time

Threats to the Great Barrier Reef

Climate change - temperature, rising sea levels
Land based run-off - pesticides, detergents
Coastal development - tourism, urban development
Illegal fishing - interrupting food chains

Distribution

region where an organism is found

Abundance

density or no. individuals in that area

Factors affecting distribution & abundance

Physical - temperature, rainfall, altitude, light, soil
Biotic - food source, predators, competitors, etc.
Underpopulation - some species need min. pop. size
Chemical - pH, salinity, water
Dynamic - wind speed/patterns, wave actions

Taxonomy

the science of classifying organisms based on shared characteristics

Binomial classification

systematic classification and description of species by 2 Latin names (using binomial nomenclature)

Benefits of a classification system

Understand relationships, evolution & diversity
Internationally recognised (easy communication & access to quick information)

Linnaean system - classification system

classification based on similarity and functions of physical features

4 features of the Linnaean System

Hierarchical structure
3 kingdoms - Eukarya, Archaea, Eubacteria
Uses binomial nomenclature
Based on morphological features

Advantage of the Linnaean System

can distinguish major groups

Limitation of the Linnaean System

no information about evolutionary relationships

Linnaean System - Taxa for Eukaryotes

Kingdom
Phyla (inv. PCPAMA) (vert. BFARM)
Class
Order
Family
Genus
Species

Methods of Reproduction - classification system

classification based on how species reproduce

Sexual reproduction (methods of reproduction)

union of 2 gametes from 2 parents
External fertilisation - outside female
Internal fertilisation - inside female
Hermaphrodites - male + female organs in 1 body

Asexual reproduction (methods of reproduction)

one parent producing identical offspring
Parthenogenesis (without fertilisation by sperm)

Survivorship curves

graphical representation of species survival patterns as a function of age

Type I (survivorship curve)

high - low survivorship... few offspring receive care and nurturing (i.e.: large mammals)

Type II (survivorship curve)

steady survivorship... constant death rate over lifespan (i.e.: small rodents)

Type III (survivorship curve)

low - high survivorship... many offspring that receive little care (i.e.: fish)

Reproductive strategies (r/K selection theory)

decide the quality & quantity of offspring produced by a species

K strategy (r/K selection theory)

type I survivorship (high-low)... predictable environment, small numbers of offspring

r strategy (r/K selection theory)

type III survivorship (low-high)... unstable environment, large numbers of offspring

Molecular Sequences - classification system

systemics / molecular phylogeny - using genetic information (i.e.: DNA sequences) and molecular differences to determine relationships between organisms, both present and extinct

Phylogenetic tree

shows evolutionary relationships between both present and extinct organisms

branch lengths proportional to amount of inferred evolutionary change

CLADE

A GROUP OF ORGANISMS THAT CONSIST OF A COMMON ANCESTOR AND ALL ITS LINEAL DESCENDANTS

Cladogram

a diagram that shows evolutionary relationships between species

Assumptions of Cladistics

1. Common ancestry - all species diverged from the same common ancestor
2. Bifurcation - existing species evolved into 2 groups (2 new lineages)
3. Physical change - characteristics of organisms change over time

Biological Species Concept (BSC) - definition of species

a species is a group of organisms that can interbreed and produce fertile offspring

Limitations of the BSC

Can't test production of fertile offspring with fossils
Species don't always sexually reproduce
Some hybrids can be fertile
There is a flow of genetic material that does not involve (sexual/asexual) reproduction

Phylogenetic Species Concept (PSC) - definition of species

a species is the smallest set of organisms that share a common ancestor and can be distinguished from other sets

Limitations of the PSC

Can't apply the PSC to all forms of life
Very few groups of organisms have detailed evolutionary histories

Mules (Equus mulus) - female horse x male donkey

an interspecific hybrid that does not produce fertile offspring

Microhabitat

a small, specialised habitat within a larger habitat with unique conditions (sometimes home to unique species)

Ecosystems composed of varied habitats

microhabitat - habitat - ecosystem - biome

Ecosystem classification - management

Ecosystem classification is important in devising policies & strategies for effective ecosystem management to provide ecosystems with long-term resilience

Importance of old growth forests

provide a high level of biodiversity, maintain a wide range of ecological functions

Old growth forest management strategies

prescribed burning, government protection from logging

Importance of soil productivity

produces critical and essential macronutrients, very important for effective ecosystem management

Soil productivity management strategies

monitoring conditions

Importance of coral reefs (i.e.: GBR)

provide a megadiverse marine environment with high biodiversity

Coral reef management strategies

prohibit / limit the fishing of certain species, reduce land based run off and coastal development

Stratified sampling

dividing a population into non-overlapping subgroups (strata), then taking random samples from each stratum

Benefits of stratified sampling

- reduced error of estimation
- increased prevision for same sample size
- reduced cost of sampling

Disadvantages of stratified sampling

- population must be divided into clearly identifiable strata
- no accurate estimation of proportions of each stratum
- some strata must be joined to ensure adequate numbers

Random sampling

samples / quadrats randomly selected to record data on a population as a whole

Random vs Stratified sampling

Random sampling selects areas or parts of a population randomly without any other consideration to collect data that represents an entire population, whereas stratified sampling first divides the population into subgroups (strata) that are homogenous within, but vary between stratum, before recording data. Stratified sampling ensures that all layers or stratum are included in data analysis, whereas random does not.

Transect

a line/strip/profile for counting & mapping the number of individuals at different distances (line transect, belt transect, profile diagram)

Purpose of a transect

to identify the effect of an abiotic factor on the abundance or distribution of organisms

Quadrat

a square grid used to estimate the abundance of slow-moving or plant species in an area

Purpose of a quadrat

to determine the distribution, abundance & density of a population when total counts can't be made

4 steps to minimising bias

1. law of large numbers (more samples = increased reliability of data)
2. random-number generator
3. counting criteria (a consistent counting method
4. calibration of equipment

Autotrophs (producers)

produce all organic compounds in ecosystems by photo/chemosynthesis

Heterotrophs (consumers/decomposers)

obtain organic compounds by consuming autotrophs (primary) or other heterotrophs (secondary)

Carbon fixation

the fixation of inorganic carbon into organic molecules by autotrophs

The transfer of chemical energy along a food chain

10% transferred to next trophic level
90% used to power organisms metabolic processes

Primary productivity

productivity of autotrophs (primary producers)

Secondary productivity

production of organic matter by heterotrophs due to assimilation of food and synthesis of new cells/tissues

Gross productivity

total amount of organic matter produced

Gross primary production (GPP)

total amount of CO2 fixed by plants in photosynthesis

Net primary productivity (NPP)

the amount of energy that plants pass on to the next trophic level (after respiration and other metabolic processes have occurred)
NPP = GPP - R

Net ecosystem productivity (NEP)

amount of energy remaining after the costs of respiration by autotrophs and heterotrophs
NEP = GPP - (R0 + R1 + R2...)

Water cycle

transpiration/runoff - evaporation - condensation - precipitation - infiltration

Carbon cycle

atmosphere (respiration/combustion) - absorption (by autotrophs) - assimilation (eating along food chain) - decomposed (decomposers) / combusted (fossil fuels)

Nitrogen cycle

1. fixation (nitrogen fixing bacteria; nitrogen - ammonia/ammonium... nitrifying bacteria; ammonium - nitrate/nitrite... OR lightning)
2a. denitrification (denitrifying bacteria; nitrates/nitrites - atmospheric nitrogen)
2b. absorption (plants absorb nitrates/nitrites)
3. assimilation (nitrogen along food chain)
4. ammonification (decomposers; return nitrogen to soil in ammonia

ECOLOGICAL NICHE

THE ROLE AND SPACE THAT AN ORGANISM FILLS IN AN ECOSYSTEM, INCLUDING ALL ITS INTERACTIONS WITH THE BIOTIC AND ABIOTIC FACTORS OF ITS ENVIRONMENT

Factors determining the ecological niche of an organism

Habitat - the space an organism lives
Feeding relationships - food and food avaliability
Interspecific interactions

Competitive Exclusion Principle

2 species cannot occupy the same ecological niche (competing for the same limited resources)

If 2 species occupy the same niche, competition will show that one species has a competitive advantage. The less-favoured species must either adapt (natural selection) or will become extinct

KEYSTONE SPECIES

A PLANT OR ANIMAL THAT PLAYS A UNIQUE AND CRUCIAL ROLE IN THE WAY AN ECOSYSTEM FUNCTIONS

Importance of keystone species

- occupies a crucial role in the food web of an ecosystem
- removal of the keystone species would have a dramatic effect (proportions of species would be imbalanced)
- removal of the keystone species will likely cause the ecosystem to collapse

Examples of keystone species

Cassowary - eats fruit and is main dispersal agent for many plants
Northern Quoll - keystone predator (eats insects, reptiles, small mammals, and fruits)
Acorn Banksia - only source of nectar for honeyeaters at some times of year (honeyeaters important for pollination of plants)

CARRYING CAPACITY

THE SIZE OF THE POPULATION THAT CAN BE SUPPORTED INDEFINITELY ON THE AVAILABLE RESOURCES AND SERVICES OF AN ECOSYSTEM

Biotic factors limiting carrying capacity

- competition for resources
- predation
- disease

Abiotic factors limiting carrying capacity

- space
- availability of nutrients
- pollution / natural disasters
- extreme climactic events (i.e.: drought / temp. change)

Density dependent factors limiting carrying capacity (determined by population size)

- competition for resources
- predation
- space / crowding
- infectious disease / parasitism