Selection pressures are all the factors of an ecosystem that
influences changes of survival
Natural selection is a process whereby species which have traits
that enable them to adapt in an environment survive and reproduce, and
then pass on their genes to the next generation.
Drives natural selection
Those individuals within the population that have random variations
that make them better suited to survive in the changed environment are
more likely to survive
Genetic based variation are passed from presurvung parents to
offspring
Biodiversity is essential for a surviving population → If all
organisms were the same, no organisms could adapt to new conditions. -
Abiotic pressures:
Temperature
Light intensity
Pressure
Salt concentration
Water availability
Biotic Factors
Competition
Prey Availability
Predation
Abundance and Distribution
Abundance → How many individuals of that species live throughout
an ecosystem
- Distribution → Where it is found
Both abiotic and biotic factors affect these
Ecology
The study of interrelationships between different types of
organisms and between organisms and their environment.
Determines the distribution and abundance of flora and fauna
Determines measures of populations in areas
Studies the patterns that are formed → Increase or decrease in
population
What factors influence the distribution and abundance of populations
in ecosystems?
Measuring Plant Abundance
Non mobile organism are easier to collect data about
120 daises have been collect in 10 1mx1m quadrats. What is the
estimated abundance of daises in that area
(120/1x10) x 800
Measuring Animal Abundance
Mark, Release, Capture
First sample, 20 individuals were marked. Second sample 50 were
collected, 10 were marked.
(20x50/10)
Population Trends
Examining population trends can lead to inferences about the
species and what abiotic and biotic characteristics they are
most suited too.
Changes in Populations Over Time
Members in population that survive and reproduce in their
habitat carry the traits most suitable for the conditions
Cane Toads
Introduced to Australia in 1935 to control the greyback cane beetle
in sugar plantations
Increasing at a fast rate
Specific structural adaptations and behaviours to suit Australia
Feed at night, no predators, breed all year, absorb water through
skin.
The Cane Toads are evolving to be faster, but more prone to arthritis
Predators have increased resistance to the toxin and those reluctant
to eat cane toads are ones that survive and reproduce
Red Belly Black snakes have gotten smaller due to the inability to
consume the frogs → Snakes big enough to eat them die due to the toxin
The Northern Quoll has developed a Toad aversion mechanism to avoid
the consumption of the toads
Prickly Pear
Introduced to Australia to start cochineal dye industry
Due to the lack of environmental pressures prickly pears spread at a
rapid rate
Nonetheless, due to the lack of biodiversity, introducing a moth
provided a strong selection pressure that quickly reduced the numbers
and distribution of the prickly pears.
Adaptations
Inquiry Question: How do adaptations increase the organism’s ability
to survive?
Adaptations
Organisms are adapted to survive in their natural environment as
a result of evolutionary change by natural selection
An adaptation is a characteristic that an organism has inherited and
makes it suited for its environment
It is a result of change that arise via mutation, when a cell
divides and replicates during the process of reproduction
Structural Adaptation
How an organism is built
Physiological
How an organism functions
Behavioural
How an organism acts and behaves
Structural Adaptation- Plants
Desert plants are able to balance photosynthesis and water for
cooling purposes without risking dehydration
Xenophytes → Structural adaptations to maximise absorption and
storage or water and minimal loss of water
Eucalypts → Waxy leaves to minimise transpiration of water and
exposure to sunlight
Cypress Pines → Tiny cylindrical leaves to have a small SA:V ratio
Structural Adaptations- Animals
Thorny Devil
Has spikes on its body to make it look more ferocious as well as
being harder to swallow by prey
Has scales that absorb water straight into its mouth
Gold and brown camouflages in dessert
Wombat
Muscular shoulders and large claws used for extensive digging -
Pouch to protect joeys from dirt whilst digging
Physiological Adaptations- Plant
Salt tolerant plants are able to maintain metabolic functioning
through their cells accumulate sodium and chloride ions
Minimise salt toxicity by increasing water content in vacuole
Physiological Adaptations- Animal
Penguins, seals and polar bears convert a lot of their diet to a
fat layer to insulate them from the cold
Some animals slow down their metabolic rates so their overall
temperature is cooled
Cane toads dig a water tight mucus cocoon for cooling
Behavioural Adaptations- Plant
The venus flytrap has adapted to live in nitrogen-poor soils
which it obtains via insects
It can act rapidly when it detects an insect
Insect becomes trapped and the plant absorbs its nutrients
Behavioural Adaptations- Animal
Puffer fish pumping air into their stomachs and blow up twice
their size to frighten predators
Penguins route in packs to reduce time spent in the cold
Darwin in the Galapagos Islands
Dariwn observed small ground finches on the Galapagos Islands
The shape of their beak was observed → Size of beaks differed
Naturally occurring changes in colour, beak size and leg length
Depending on which island they lived on, and the conditions they
found themselves in, some birds thrive and reproduced - Charles Noted:
There is a variation in all populations with many variation heritable
There are more organisms born then the environment can sustain
Those individuals that have more suitable characteristics survive
Survivors pass on traits to offspring
Favorable traits will become more numerous if the environment is
stable
Survival of the Fittest
Variation exists with more population
More offspring are produced that can survive
The offspring better adapted will survive and reproduce
The favourable characteristics are passed on
Overtime favourable characteristics will increase in the population
Theory Of Natural Selection
Inquiry Question: What is the relationship between biodiversity and
evolution?
The Theory Of Evolution By Natural Selection
Diversity allows adaptations to change in an environment
Species have been developing for billions of years
All theories of evolution share a common basic premises
Living organisms arose from common ancestors or a common life form
and have changed over time
Differences that occur among groups of living organisms imply that
living things change over time
Similarities occur in living things and suggest a common ancestry;
the basic chemistry, inherited from a common life form, has remained
relatively unchanged and has been passed down through generations.
Biological Diversity
The variety of forms of life on Earth, the diversity of the
characteristics of living organisms and the variety of their
ecosystems.
Diversity allows for adaptations
Three levels of biodiversity
Genetic → Genetic makeup in a species
Species → Measure of the diversity of species
Ecosystem → Variation of different ecosystems
Genetic Diversity
Important for the population to be able to adapt
Environments are constantly changing and pose selection pressures
that enable some organisms with favourable characteristics to survive
and reproduce
No variation in the population will be more detrimental for an
invasive organism or pressure
More genetic diversity = more chance of survival
Concept of Natural Selection
Organisms must possess traits that favor their survival in that
environment
[Variability] → All populations have random differences
or variations among members
[Heritability] → Variation must be inherited
[Over Reproduction] → Organisms produce more offspring than
what the ecosystem can sustain
[Competition] → The best suited traits will ultimately thrive and
reproduce
If there is a sudden change in the environments, those individuals
that randomly possess a variation that is an advantage are more likely
to survive the changed conditions
Diversification of Life on Earth
The move form unicellular organisms to multicellular organs
began when these cells clustered together
Life began to diversify further with a rise in invertebrates to fish
and amphibians
Followed by the dominance of reptiles
Mammals species then began to dominate
Selection pressures lead to the thrive and extinction of species
Microevolution vs Macroevolution
Macroevolution → Takes place over millions of years, usually
results in new species
Microevolution→ shorter periods and results in changes of a
particular species, but does not create a new species
Small changes can lead to a dramatic difference
New varieties or races (Dog Breeds)
Evolution Of The Horse
Has a complete fossil record
Mammal belonging to the family Equidae
Evolved over 50 million years from a dog-sized, forest-dwelling
animal Hyracotherium
Shares a common ancestor with tapirs and rhinoceroses
Horse evolution has a branching nature (rather than a linear
evolution)
The fossil record showed there were several different migrations,
changes in trends from smaller to larger sizes as well as reduction in
size. The rate of evolutionary change did not appear to be constant.
Fossils have shown changes in body size, number of toes and
dentition (teeth - development of grinding surfaces)
Genetic variation caused by mutations, natural selection, genetic
drift and speciation have all contributed to the evolution of the
horse
Microevolution can occur when a series of mutations leads to a
change in gene frequency in a population. This change in the gene pool
is due to chance and is called genetic drift. If a population becomes
isolated speciation might occur.
A small population with a mutated gene may become separated from the
main population, causing the mutated gene to increase in the
population as interbreeding occurs. If the change is favourable it is
selected for (it increases chance of survival)
The isolated population evolves to become significantly different
from the original population and eventually if brought back together
they would not be able to interbreed, resulting in the formation of a
new species.
Evolution Of The Platypus
Platypus shows similar features to birds, reptiles and mammals -
Webbed feet, venom gland, hair on body
Genetic evidence suggest that monotremes split off first evolved
The first split was between marsupials and mammals
Platypus and echidna share common ancestors
Very well adapted to the environment it lives in
Lay an egg with yolk
Platypus can located prey with their eyes closed, by sensing
electric pulses given off by muscles
- A type of macroevolution
Convergent Vs Divergent Evolution
Convergent
Distantly related species which have moved to similar environments
and are exposed to similar selection pressures to evolve similarly
Similar habitats, similar variation would be favoured by natural
selection to enable them to survive
Divergent
Ancestral species radiates into a number of descendant species with
both similar and different traits
Usually influenced by various selection pressures
An example is Darwin's finches
Gradual Natural selection vs Punctuated Equilibrium
Gradualism
Populations slowly diverge by accumulating changes in
characteristics due to selection pressures
Suggest that transitional forms should exist
Common ancestor
Small variation
Punctuated Equilibrium
Occurs in short bursts of rapid change, followed by long period of
stability within populations
Mutations are passed on
Evolution- The Evidence
Inquiry Question: What is the evidence that supports the Theory of
Evolution by Natural Selection?
Biochemical Evidence
All living things share the same macromolecules such as proteins
and DNA and biochemical process such as cellular respiration
Biochemistry is the study of chemicals found in sound
More closely related species have more similar DNA and proteins
Similarities imply they had a common ancestor
Amino Acid Sequencing
Proteins are a component of all living organism
Made up of amino acids
The sequence of amino acids in the protein is analysed and
similarities and differences between organisms are identified.
Differences imply the organism has evolved.
Number of differences is proportional to the length of time since
the organism separated
DNA Hybridisation
Samples of DNA are removed from two different organism
The separated strands of the species to be compared are then mixed.
The two strands combine (reassociation) and form a ‘hybrid’ DNA
molecule
The more closely matched the DNA, the tighter the binding.
Heat is applied to determine how tightly the DNA strands have
combined. More closely related species have more similar sequences of
bases and therefore the strands bind tightly.
DNA Sequencing
The exact order of bases in DNA of one species is compared with a
similar fragment of another species.
A piece of DNA is isolated from each organism.
Multiple copies are made, and dye is used to label the bases.
A DNA sequencer is used to graph and print out the sequence of
bases, which are then compared.
Organisms that share a common ancestor share fewer differences.
Provides more detailed information than other biochemical methods.
Comparative Anatomy
Study of similarities and differences in the structure of living
things
More similarities imply the organism have separated from a common
ancestor recently
Homologous Structures (Divergent Evolution) - Differences in
structure represent modification.
Organisms that have the same basic plan to their structure but show
modifications are called homologous – they have the same evolutionary
origins.
Analogous Structures (Convergent Evolution)
Structures that look similar but are very different (e.g. wings of
bird and wings of grasshopper)
May have started off differently but over time evolve to look similar.
E.g. Australian Echidna and European Hedgehog
Do not show evolutionary relatedness – shows the evolution of
structures for a common purpose.
Vestigial Structures
Evolutionary remnants of body parts that no longer serve a useful
function.
Provides evidence of common ancestry.
E.g. presence of coccyx and appendix in humans.
Comparative Embryology
Comparison of development stages of an organism
Related species show similarities in development
Fish, mammals, amphibians, birds
Biogeography
Study of the distribution of organisms
For a new species to arise, it must be genetically isolated.
Fossil Evidence
Fossils provide direct evidence of the existence of an organism
in the past
The sequence in which fossils are laid down in a rock reflects the
order in which they were formed
Law of Superposition
Further down in a rock represent an older fossil
Relative dating relies on the assumption that the fossils higher up
in the rock are younger than the lower fossils → Fossils are dated
relative to one another
Absolute dating enables the actual age of the specimen to be
determined by using radioactive elements that are present
Modern Day Evolution
Cane Toad
Faster and larger cane toads have reproduced more, hence the whole
population is slowly getting faster
Red-belly black snakes have developed a smaller mouth so they are
incapable of consuming the organism
There are no selection pressures on the cane toad, hence they will
be able to continue to reproduce at exponential rates.
Antibiotic resistant Bacteria
Antibiotics are chemical that inhibit the growth of bacteria or
destroy them → Target cell wall and inhibit cell metabolism
When penicillin and other antibiotics were introduced the threat
posed by infections was reduced
However, strains of bacteria has developed that are not affected by
antibiotics
The bacteria that survives passes on genes which leads to a whole
new variation of bacteria
Module 4 - Ecosystem Dynamics
Population Dynamics
Inquiry Question: What effect can one species have on the other
species in a community?
Organisation within ecosystems
Biosphere contains all the living thighs on Earth
Environments can positively or negatively impact an organism - An
organism living and non-living surrounds its ecosystem
Impact of Abiotic Factors
Abiotic factors are not easily disturbed
Own unique way of thriving within the limits of the abiotic
environment
Water is a very effective filter of sunlight
Rapid drop in temperature
Oxygen levels
Impact Of Biotic Factors
Living organisms can affect each other by predation and
symbiosis but also have an equally profound effect on resources
Food sources, mates, light, nutrients, water
Predation
Predator obtains its food by killing and eating another animals
Found in aquatic or terrestrial ecosystems
Spider capturing bugs in its web and eating it
Competition
Competition is usually for a resource in the environment that is
limited supply but valuable for survival
All competition involves risk to the competitors and the rewards
must outweigh the inherent risk
Intraspecific → Within a species
Interspecific → Between species
Symbiotic
Interactions in which two organisms live together in a close
relationship that is beneficial to at least one of them
Obligate relationship → species depend on each other to live
Mutualism
Both organism benefit
Clownfish and sea anemone → Clown fish is protected by the sea
anemone whilst the fish cleans the plant
Commensalism
One species is benefited whilst the other is not harmed or helped
Birds that live in hollow holes in trees
Parasitism
One species benefits whilst the other is harmed
Parasite obtains shelter from the host organism while feeding upon
the tissue and fluids
Ecological Niches occupied by Species
The part of an ecosystem that the organism occupies is called a
niche
Refers to all the resources that a species uses, including biotic and
abiotic
The process of having unique living strategies
Fundamental niche → The perfect conditions and resources for an
organism to live and reproduce
Realised Niche → All the aspects of the ecosystem including the
interactions of other species
Consequences in ecosystems
Predation
Effect the distribution and abundance of prey
If the prey can reproduce fast enough, rates wont drop
- Prey and predators are in direct
proportion
Competition
Effects reproduction and survival rates
More food sources → More abundance of both species
Different traits will boost a species survival of getting resources
Symbiosis
Increased evolutionary diversification
Development of new species from the integration of genetic material
More resilient ecosystems → Biodiversity
Disease
Any process that adversely affects the normal functioning of tissue
in a living organism
Bacteria, virus, Pathogen
Alter the balance of food webs → Affected species will decline in
numbers
Recent Extinction
Climate Change
Continent dried out
Rainforests were contracting – stored moisture and returned
moisture to the atmosphere.
Eucalypt forests replaced these, and water was not as efficiently
retained.
Became hotter and drier, fires broke out due to lightning.
Plants and animals that survived the drought and fire reproduced,
changing the flora and fauna.
Arrival Of Humans
Aboriginal people arrived successful predators.
Used ‘fire stick’ farming techniques.
Introduction of dingoes may have reduced the diversity of carnivore
predators.
Level Of Nutrients
Low level of nutrients in the soil → dry
Led to smaller animals →F can be sustained on less
Evidence for this can be seen in the smaller size of mammals in
Australia compared to counterparts across the world.
Past Ecosystems
Inquiry Question: How do selection pressures within an ecosystem
influence evolutionary change?
Past Ecosystems
It is unclear when humans first became interested in fossils.
Philosophers hinted that fossils were evidence of previous life.
Law of superposition → oldest layer at bottom and newest at top.
Aboriginal Rock Paintings
Longest unbroken tradition in the world
Humans are driven by nature to record details of their existence
West Kimberly’s rock paintings
Radiometric dating is used to date the paintings
Uranium/Thorium can be used to underlying calcite formations to show
when they were formed
Types and abundance of animals depicted in paintings changed overtime
Geological Evidence
Allows reconstruction of timeline of events
Represents the course of changes in geological and fossil deposits
Banded iron Formations
Form of geochemical evidence found in Australia
Earth's atmosphere has undergone changes, change from anaerobic to
aerobic
Form of iron rich and iron poor sediments
Prokaryotes lead to an increase in oxygen concentration in the
ocean, leading to precipitation of insoluble iron oxide
Precipitate accumulated at the bottom of the ocean, forming an iron
rich layer of sediments
Great oxygenation event transformed Earth’s atmosphere
Resulted in much larger and multicellular organism→ Organisms had to
adapt to more oxygen
Palaeontological Evidence
Fossils offer clues to the selection pressures of living things like
the climate and environment at the time
Found in sedimentary rocks → Preserve evidence rather than
destroying it
Fossilised soils contain large concentrations of carbon that
indicate presence of life
Chemosynthesis is a process where organisms use inorganic compounds
available from their environment.
The fossils formed from stromalites provide valuable informationof
early orgaims and the environment in which they lived
Ice Core Drilling
Accumulation of ice layers in places such as antarctica leaves
an annual record of gas and dust in that atmosphere of that time
Scientists can drill into the ice, extract gases and reconstruct the
climate record
Increases understanding of past environments
Radiometric Dating
Process where scientists determine the age in years of a fossil,
rock or mineral
Based off the content of radioactive isotopes
Unstable isotopes change to form stable isotopes → Undergoes
radioactive decay which scientists can compare to examine the life of
the rock
More half lives → Older
Rate of decay is calculated using the age equation that
compares the abundance of the naturally occurring isotope with the
abundance of the decay product.
Gas Analysis
Scientists can use data in ice cores to reconstruct atmospheric
concentrations of certain gases, particularly CO~2~ and O~~
2.
CO~2~ is a normal part of Earth’s atmosphere along with nitrogen,
oxygen, argon and other trace gases
But CO~2~ is also considered a ‘greenhouse gas’ that traps solar
radiation keeping the Earth warm enough to sustain life
However, increasing CO~2~ in atmosphere is likely to increase
Earth’s atmospheric temperature, known as the ’enhanced greenhouse
effect’ or ‘global warming’
Scientists use ancient CO~2~ levels~~ to infer past climates -
warming or cooling would have a direct effect on the types of plants
and animals that are suited to survive in such a climate
Oxygen has three naturally occurring isotopes: ^16^ ^^O, ^17^
^^O and ^18^ ^^O which are incorporated into water molecules. The
ratio of ^18^ O/^^^16^ ^^O in analysed ice core samples indicates
ancient water temperatures which scientists can use to reconstruct
water temperatures on Earth.
Small Mammals
We Can use fossil of past animals to show similarities and
differences to present day animals and therefore propose
evolutionary relationships between them.
When comparing the modern platypus to fossils, body shape became
smaller + more simplified.
We can infer a change in diet as dentition is different
Habitat reduced in size → May have become vulnerable.
Reasons for Change
Australia’s change in climate due to the split of Gondwana
Climate change
Arrival of indigenous
Introduction of non native plant + animals → invasive species →
Destroys or affects the natural food web
Future Ecosystems
Inquiry Question: How can human activity impact an ecosystem?
Human Induced Species
Increasing Population
Selective breeding, use of fertilisers, pesticides and herbicides
Medical breakthroughs with antibiotics, better hygiene and
vaccinations
Increasing populations of humans lead to an increase of the demand
of resources from ecosystems
Selective breeding limits the biodiversity of species, hence making
them more susceptible to being majorly effected by disease or change
Agriculture
Removal of trees leaves the soil vulnerable to erosion → Loss of
valuable minerals for an ecosystem
Pollutions harms the water and atmosphere
Irrigation was developed alongside the domestication of plants
Selective breeding of crops and livestock radically altered their
features to favour large yields
Introduced Species
Many invasive species out compete native species for light, water,
habitats and nutrients
Change the environments to alter the microclimate of the areas to
favour their own development
Completely alter the food web system which has detrimental effects
on the rest of the ecosystem
Land Clearing
Refers to the removal of native vegetation for urban and
agricultural development
Removes nesting and habitats of native animals → Cannot reestablish
anywhere else.
Extinction
Habitat loss is the leading cause of extinction
Most historic extinctions have occurred on islands because a small
habitat loss has devastating effects
Extinction opened niches for surviving organism to expand into →
Rapid development of species
Past To Inform the Future
Can estimate rates of extinction by studying recorded extinction
events, examining fossil record and by analysing modern trends
in habitat loss
Over exploitation of resources → Harvesting an amount that is not
sustainable over time
Introduced species → New species effect relationships due to
competition, predation and disease
Disruption of ecological relationships → loss of available niches
alter the distribution and abundance of species
Biodiversity
Genetic diversity → Intraspecies diversity in traits that makes
a population resilient to environmental changes
Species Diversity → Variety of species in an ecosystem
Ecosystem diversity → Variety of ecosystems available in a broader
area such a continents or globally
Climate Change
Greenhouse Effect
Solar radiation reaches and penetrates earths atmosphere
Some energy is trapped and absorbed into the land and ocean
Keeps earth warm and sustainable
Enhanced Greenhouse
Increase of concentration of greenhouse gases
More energy being absorbed in oceans and land
Warmer climate
External factors → Solar input from the sun, Earths variety in orbit
Internal factors → Active release of CO2 from volcanoes, diffusion
of CO2 from ocean, less reflection of light from ice (Melting ice is
bad)
Human Factors → burning fossil fuels, agriculture, land clearing
Models Predicting Biodiversity
Resources increase slow
Humans grow quick
Humans will outgrow their ability to feed themselves
Greater fertility will lead to starvation
Keep numbers and population in check
Mining Sites
Required to follow laws and strict guidelines, which include
submitting information on how they intended to ensure minimal
harm to environment
All mining companies must complete an environmental impact statement
as a part of their license application
Land Degradation and Agriculture
Marked improvement in the management of Australiansoils and
waterways
Farm owners can have their land inspected by scientists
Management of salinity and erosion are high priorities
Biological controls are being used to maintain pests
