BIOLOGY UNIT 3 AND 4 QCAA

Explain how environmental factors limit the distribution and abundance of species in an ecosystem.

Limiting factors are aspects of the environment that restrict an organism's ability to live there. Limiting factors can be biotic, such as species interactions, food, and water or abiotic, such as light intensity, and climate. The distribution of species is limited by their ability to access adequate food sources and habitats with optimal climate. They will be limited to areas where these factors are beneficial for their survival. The abundance of species is limited by the abundance of food, water, light intensity, and shelter in the areas with beneficial factors.

Describe the Linnaean classification system

· Hierarchical rank-based structure of classifying organisms

· 3 domains (archaea, bacteria, eukarea)

· Uses binomial nomenclature

· Uses morphological features of organisms to create groups according to their similarities and features

Describe sexual and asexual reproduction

Asexual involves one parent, gametes are not produced, offspring is genetically identical to parent, cell division it mitotic and large number of offspring is produced.

Sexual involves two organisms, gametes are produced, offspring has genetic variation, gametes are produced by meiosis and small number of offspring

Describe r and K methods of classification

r. value high r value, low K value, grow fast, minimal life expectancy, high number of offspring, low parental care, population controlled by density independent factors such as climatic events or fires.

K. value high K value, low r value, grow slower, high survival rate, high life expectancy, fewer offspring and invest more in parental care, population is controlled by density dependant factors such as competition or predation

Describe the classification system for molecular sequences

Molecular phylogeny is a branch of phylogeny that analyses genetic and heredity molecular differences predominantly in DNA sequences to gain information on organisms' evolutionary relationships, also called cladistics. If an organism has a similar set of DNA sequences, proteins, or chromosomes it provides evidence that the two organisms shared a common ancestor.

Define the term clade

A group of organisms that consists of a common ancestor and all its lineal descendants

Recall the common assumptions of cladistics

1. Common ancestry - all organisms came from one common ancestor through reproduction

2. Bifurcation - when a lineage splits it divides into two groups

3. Physical characteristics - there is a change in physical characteristics occurring in lineages over time

Recognise the need for multiple definitions of species

There are multiple concepts of species, for example biological, morphological and phylogenetic and they all have different definitions of species based on their different classification process

Identify one example of an interspecific hybrid that doesn't produce fertile offspring

Mule (Equus mulus)

Explain classification of organisms according to predation

An interaction in which one organism kills (predator) another for food (prey).

Explain classification of organisms according to competition

Competition within and between species is a common feature of all communities, organisms can be classified by how they compete with one another.

Explain classification of organisms according to symbiosis

Symbiosis is an interspecific interaction in which species live together in a long-term relationship:

1. parasitism is when one species benefits at the expense of another;

2. mutualism is when both species benefit from the interaction;

3. commensalism is when one species benefits and the other isn't benefited or harmed.

Explain classification of organisms according to disease

Disease is where species can be vectors, transmitting diseases to other species.

Explain how the process of classifying an ecosystem is an important step towards effective ecosystem management

· classifying ecosystems enables for decision making about the ecosystem's management

· decisions serve a range of values such as cultural, recreational and economic therefore agreeing on classification is important

· classification enables stakeholders to prescribe an effective management technique

· classification supports long term ecosystem resilience

Describe the process of stratified sampling

1) Purpose (estimating population, density, distribution, environmental gradients and profiles, zonation, stratification)

2) Site selection

3) Choice of ecological surveying technique (quadrants, transects)

4) Minimising bias (size and number samples, random number generator, counting criteria, calibrating equipment, and noting associated precision)

5) Methods of data presentation

Sequence and explain the transfer and transformation of solar energy into biomass as it flows through biotic components of an ecosystem

Plants convert solar energy into biomass through photosynthesis. Photosynthesis converts light energy into chemical energy. Once plants die, they release carbon dioxide into the air which can be absorbed by other photosynthesising plants.

Describe the transfer and transformation of water as it cycles through the ecosystem

Precipitation > evaporation/transpiration > condensation

Describe the transfer and transformation of carbon as it cycles through the ecosystem

· Photosynthesis: plants absorb CO2 from the atmosphere (only process that decreases atmospheric CO2)

· Feeding: moves carbon in biological molecules along food chains

· Respiration: when living organisms respire, they release CO2 into the atmosphere

· Fossilisation: some dead organisms get compressed over millions of years and form fossil fuels or carbon stores such as limestone

· Weathering: acid rain can dissolve limestone, releasing CO2

· Combustion: when fossil fuels are burned, CO2 is released into the atmosphere

· Excretion: carbon compounds are excreted in urine, broken down by decomposers

· Egestion: carbon is egested in faeces, broken down by decomposers

· Decomposition: carbon compounds in dead organisms, urine, and faeces are broken down by decomposers (bacteria or fungi)

Describe the transfer and transformation of nitrogen as it cycles through the ecosystem

1) Nitrogen fixation - lightening converts nitrogen in the air to nitrates by bonding with oxygen and then dissolving in rain OR nitrogen gas is converted into ammonia or ammonium by nitrogen fixing bacteria in soil or root nodules of legumes or clover plants

2) Assimilation - plants absorb nitrates from the soil and these build up proteins. The plant may be eaten by an animal and its biomass is used to produce animal protein

3) Ammonification/nitrification - urea and faeces are broken down by decomposers. This results in nitrogen being returned to the soil as ammonia or ammonium, then converted to nitrites then nitrates by nitrifying bacteria in soil.

4) Ammonification/nitrification - decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia and ammonium, then converted to nitrites then nitrates by nitrifying bacteria in soil.

5) Denitrification - bacteria in the soil break down nitrates by liberating oxygen and returning nitrogen gas to the air, usually in waterlogged soil.

Define ecological niche in terms of habitat, feeding relationships and interactions with other species

The role and space that an organism fills in an ecosystem, including all its interactions with the biotic and abiotic factors in its environment

Understand the competitive exclusion principle

No two species can occupy the exact same niche in an ecosystem

Define keystone species and understand the critical role they play in maintaining the structure of a community

Define

A plant or animal that plays a unique and crucial role in the way an ecosystem function.

Understand

Keystone species have a large influence over the stability and biodiversity of the whole community, including species they dot directly interact with. A keystone species isn't necessarily the most abundant species, nor the top-level predator but their presence prevents any one species from monopolising space and resources in the area.

Define the term carrying capacity

The size of the population that can be supported indefinitely on the available resources and services of that ecosystem.

Explain why the carrying capacity of a population is determined by limiting factors (biotic and abiotic)

A limiting factor is an abiotic or biotic factor that restricts the number of individuals in a population. Carrying capacity is the size of the population that can be supported indefinitely on the available resources and services of that ecosystem. When limiting factors are favourable, for example when there is plenty of food, shelter and water, birth rates can increase, and death rates will decrease. The abundance of resources and decreased competition allows for an increase in population numbers, therefore, increasing the carrying capacity.

Calculate population growth rate and change using birth, death, immigration and emigration data

Population growth rate =

(birth rate + immigration rate) - (death rate + emigration rate)

Use the Lincoln index to estimate population size from a secondary or primary data

Where N = population

M = number of individuals caught, marked, and released initially

n = number of individuals caught on second sampling

m = number of individuals recaptured that were marked

Analyse the population growth data to determine the mode of population

J curve

· Exponential

· Represent numbers that increase more over time

· If resources were unlimited, populations would continue growing exponentially

S curve

· Logistic

· Basically, a J curve but with a 'ceiling' in the form of the carrying capacity

· Since resources are always limited and ecosystems can't sustain an infinite amount of organisms an S curve is typically used to model real world populations

Discuss the effect of changes within population-limiting factors on the carrying capacity of the ecosystem

When the abiotic and biotic population-limiting factors change, this can cause the carrying capacity increase or decrease. If the abiotic resources are abundant, the population could expand rapidly causing the carrying capacity to also increase and vice versa. If biotic factors change such as a species is removed from the ecosystem it could cause the carrying capacity to increase or decrease depending on what interactions the removed species had with other organisms in the community.

Explain the concept of ecological succession (refer to pioneer and climax communities and seres)

Ecological succession is the process of change within an ecosystem and how the species diversity may shift over time. It can be either primary (changes in an entirely new habitat) or secondary (changes in a place that was previously a functioning ecosystem but was disturbed or damaged). Pioneer species are plants that first colonise the ecosystem, they are defined on their ability to photosynthesise, fixate nitrogen, tolerate extreme conditions, and rapidly germinate or reproduce. An ecosystem undergoing succession will reach a climax community when the ecosystem is stable and balanced. A seral community (sere) is an intermediate stage in an ecosystem advancing through different stages of succession.

Differentiate between the two main modes of succession: primary and secondary

Identify features of pioneer species that make them effective colonisers

Ability to:

· Fixate nitrogen

· Photosynthesise

· Tolerate extreme conditions

· Rapidly germinate or reproduce

Analyse ecological data to predict temporal and spatial successional changes

The most accurate and comprehensive data set would entail every part of the ecosystem, such as a census collection. However, this is highly impractical for most ecosystems. A more practical approach is to examine parts of the ecosystem through random sampling. Ecosystem models are useful representations of elements within the ecosystem, the relationship between the elements and the relationship with surrounding ecosystems. Could be based on r & K species, biodiversity, biomass or changes in biotic and abiotic factors.

Predict the impact of human activity on the reduction of biodiversity and on the magnitude, duration, and speed of ecosystem change

Human activity has reduced biodiversity and has an impact on the magnitude, duration, and speed of ecosystem change.

· Overexploitation: harvesting species or resources from the wild at rates faster than natural populations can recover. Includes overhunting and overfishing

· Habitat destruction: when natural habitats are no longer able to support the species present, resulting in displacement or destruction of its biodiversity. Includes harvesting fossil fuels, deforestation.

· Monocultures: agricultural practice of growing a single crop, plant, or livestock species, variety or breed in a field or farming system at a time. Planting the same crop in the same place each year removes nutrients from the earth and leaves the soil weak and unable to support healthy plant growth, in addition decreasing biodiversity.

· Pollution: pose a serious threat to biodiversity, with issues affecting biodiversity in Australia generally being categorised as relatively local in nature (specific waste from poorly managed activities) or relating to broad landscape process (nutrient enrichment in the Great Barrier Reef from farming or inappropriate pesticide use).

· Urbanisation: reduced biodiversity and dominated by humans. Little recycling of matter, large amounts of energy and matter required to maintain modern standards of living. Increase in gaseous and material waste that are disposed into the atmosphere and on the land and in the water of other ecosystems.

Understand DNA

Deoxyribonucleic acid (DNA) is a double-stranded molecule that occurs bound to proteins (histones) in chromosomes in the nucleus in eukaryotic cells and as unbound circular DNA in the cytosol in mitochondria and chloroplasts of prokaryotic cells.

Recall the structure of DNA

A single nucleotide is made up of a five-carbon sugar (deoxyribose), a negatively charged phosphate group and a nitrogenous base. Nitrogenous bases are complimentary: adenine is with thymine and guanine is with cytosine; and are held together by hydrogen bonds. The nucleotides are linked together by phosphodiester bonds. DNA has anti-parallel structure where one strand follows the 3' to 5' direction and the other strand follows the 5' to 3' direction.

Explain the role of helicase and DNA polymerase in the process of DNA replication. Reference to direction of replication

Helicase is an enzyme which unwinds the double helix by breaking the hydrogen bonds between the complimentary base pairs, hence, separating the strands. DNA polymerase is an enzyme that is responsible for making exact copies of existing DNA fragments, hence forming new DNA strands. The leading strand (the one that gets copied runs in a 3' to 5' direction and the DNA polymerase attaches nucleotides in the 5' to 3' direction. The outcome of DNA replication is two double helix molecules, each consisting of one parental strand and one new strand.

Within the process of meiosis I and II:

· Recognise the role of homologous chromosomes

In meiosis I and II homologous chromosomes are formed by joining one chromosome from each parent, they share the same centromere, gene loci, gene sequence, and length. Produce genetic sequences for offspring

Within the process of meiosis I and II:

· Describe the process of crossing over and recombination and demonstrate how they contribute to genetic variation

Recombination occurs in prophase 1, it is when homologous chromosomes 'cross over'. The recombination scrambles the maternal and paternal genes from each homologous chromosome and rearranges the combinations of alleles available on each homologous chromosome. As a result, the genetic diversity of offspring increases because of the new combinations of genes.

Within the process of meiosis I and II:

· Compare and contrast the process of spermatogenesis and oogenesis

Both oogenesis and spermatogenesis are processes of sex cell production however spermatogenesis occurs in males and produces sperm cells and oogenesis occurs in females and produces ovum. In oogenesis, cytokinesis in both meiosis 1 and 2 is unequal and produces only a single diploid egg and small polar bodies that degenerate. By contrast meiosis in spermatogenesis produces four haploid sperm. At birth, an ovary contains all the cells that will ever develop into eggs. Once puberty is reached, sperm cells are produced throughout a man's life. Sperm are produced continuously, whereas oogenesis has long breaks between stages of division. This is because all primary oocytes begin meiosis in the female embryo, but some eggs will not complete meiosis 1 until the woman reaches menopause.

Demonstrate how the process of independent assortment and random fertilisation alter the variations in the genotype of offspring

Independent assortment occurs in metaphase 2. It is the process where maternal and paternal homologous chromosomes align independently of one another. In so, the resultant haploid cell contains a mixture of genes from the mother and father. As the homologous pairs carry different genetic information, independent assortment increases the number of different combinations of genes carried by the gametes.

Random fertilisation also increases the possible outcome of alleles inherited by the offspring. This is because any egg can be fertilised by any sperm and produce a completely genetically random genotype of the offspring.

Define the term gene

Region/s of DNA that are made up of nucleotides, the molecular unit of

Define the term genome

All genetic material in the chromosome of an organism, including its genes and DNA sequences

Understand that genes include coding and non-coding DNA

Genes include coding and non-coding DNA. Coding DNA includes exons, and they are the regions in our genes that go on to create proteins. Non-coding DNA includes functional RNA, centromeres, telomeres, and introns and are not directly involved in protein synthesis. Many functions of non-coding DNA are yet to be determined.

Explain the process of protein synthesis in terms of transcription and translation

Protein synthesis is the process in which cells make proteins. It occurs in two stages: transcription and translation.

Transcription involves copying a gene’s DNA sequence to make an RNA molecule. This is performed by enzymes called RNA polymerase, they link nucleotides to form an mRNA strand. In the process of translation, the mRNA formed in transcription is transported out of the nucleus to the ribosome. Here, it directs protein synthesis. The mRNA passes through the ribosome and the tRNA interacts with it, adding ammino acids together to make a protein chain.

Recognise that the process of gene expression

The process of gene expression is to synthesise a functional gene product (protein or functional RNA. The process can be regulated and is used by all forms of life

Identify that there are factors that regulate the phenotypic expression of genes

· During transcription and translation

During transcription

Chemical modification of chromatin, direct chemical modification of DNA

During translation

Regulation of gene expression (switching gene off after transcription to prevent translation)

Identify that there are factors that regulate the phenotypic expression of genes

· Through products of other genes

Regulatory proteins, transcription factors, activating proteins and repressing proteins

Identify that there are factors that regulate the phenotypic expression of genes

· Via environmental exposure

Epigenetics is the study that a variety of environmental factors can influence gene expression. The changes in gene expression, the changes in gene expression can be passed onto offspring. For example, the colouration of agouti mice is directly linked to the methylation levels of the mother

Recall an example of a transcription factor that regulates morphology and cell differentiation

HOX and homebox transcription factors regulate morphology. The SRY (sex-determining region of the Y chromosome) gene regulates cell differentiation

Identify how mutations in genes and chromosomes can result from errors in:

· DNA replication (point and frameshift)

A mutation is a change in a gene or chromosome relative to the original.

Point mutation is when DNA polymerase mismatches bases accidentally and that can result in a mutation. A frameshift mutation is when an additional nucleotide is added or is not added. Both processes lead to disruption of further amino acid triplets placing them out of frame.

Identify how mutations in genes and chromosomes can result from errors in:

· Cell division (non-disjunction)

Non-disjunction is the failure to separate. In meiosis failure of homologous chromosome pairs to separate during anaphase 1 or of the sister chromatids in anaphase 2 can result in an extra chromosome or one less chromosome which is aneuploidy

Identify how mutations in genes and chromosomes can result from errors in:

· Damage by mutagens (physical, inc. UV radiation, ionising radiation and heat and chemical)

Physical mutagens (UV radiation, ionising radiation and heat): can damage the DNA

Chemical mutagens: if a large number of chemical mutagens interact directly with DNA it can become carcinogenic.

Explain how non-disjunction leads to aneuploidy

Non-disjunction is when the chromosomes or sister chromatids fail to separate in anaphase 1 and 2. Aneuploidy is the presence of one or more extra chromosomes or the absence of one or more chromosomes. If non-disjunction occurs, meiosis will result in one or more extra chromosomes or the absence of one or more chromosomes, therefore aneuploidy.

Describe how inherited mutations can alter the variations in the genotype of offspring

if a cell fails to eliminate affected cells or reverse mutations for germline cells, then these mutations will be inherited by gametes and ultimately offspring. All phenotypic variation is affected by the presence or absence of specific proteins and the actions of those proteins.

Define polygenic inheritance

Polygenic inheritance is when one characteristic is controlled by two or more genes

Describe the process of making recombinant DNA

· Isolation of DNA, cutting of DNA (restriction enzymes)

· Insertion of DNA fragment (plasmid vector)

· Joining of DNA (DNA ligase)

· Amplification of recombinant DNA (bacterial transformation)

Recognise the applications of DNA sequencing and DNA profiling

DNA sequencing is performed to map species' genomes and DNA profiling is performed to identify unique genetic information

Explain the purpose of polymerase chain reaction (PCR) and gel electrophoresis

PCR is a cyclical reaction in which DNA polymerase is used to copy a DNA template, making millions of copies of the same piece of DNA. The purpose of PCR is to amplify DNA.

Gel electrophoresis is a technique that separates DNA fragments according to their size and charge. Its purpose is to separate DNA to compare to other DNA samples or to diagnose medical disorders/illnesses.

Define evolution

Evolution is the change in genetic composition of a population during successive generations, which may result in the development of new species

Define microevolution

Microevolution is the small-scale of variation of allele frequencies within a species or population, in which the descendant is of the same taxonomic group as the ancestor

Define macroevolution

Macroevolution is the variation of allele frequencies at or above the level of species over geological time, resulting in the divergence of taxonomic groups, in which the descendant is in a different taxonomic group to the ancestor

Determine episodes of evolutionary radiation and mass extinctions from an evolutionary timescale of life on earth (3.5 billion years approx.)

Evolutionary radiation refers to an increase in taxonomic diversity or morphological disparity. Mass extinction refers to rapid and widespread extinction events of many different species.

Recognise when natural selection occurs

Natural selection occurs when the pressures of environmental selection confer a selective advantage on a specific phenotype to enhance its survival (viability) and reproduction (fecundity)

Identify that the selection of allele frequency in a gene pool can be positive or negative

Selection of allele frequency in gene pools can be positive if the phenotype is favoured in the gene pool or negative if it is not favoured

Describe the three main types of phenotypic selection: stabilising, directional and disruptive

Stabilising selection is a form of selection that tends to favour the average (middle) organisms, preserving the characteristics of the population. Directional selection tends to favour the phenotype towards one end of the bell curve. Disruptive selection tends to favour individuals at both extremes of the phenotypic range

Explain microevolutionary change through the main processes of mutation, gene flow and genetic drift

Microevolution is small-scaled change in allele frequencies within a species or population. Microevolution can occur through mutations because they are the source of genetic variation because they introduce new alleles. If the allele introduced is favoured it may lead to phenotypic change. Gene flow is the transfer of genetic material from immigration and emigration of individuals from populations. This could completely remove alleles from one location and introduce new alleles in another; this would contribute to change in allele frequencies, therefore, microevolution. Genetic drift is a change in the gene pool of a population because of chance. If alleles are added or removed from a gene pool, new alleles will form therefore creating microevolutionary change.

Recall how speciation and macroevolution occurs

Speciation and microevolutionary changes occur as a result of accumulation of microevolutionary changes over time

Identify that diversification between species can follow one of four patterns: divergent, convergent, parallel and coevolution

Divergent

A process whereby related species evolve new traits over time, away from the common ancestor to give rise to a new species.

Convergent

A process whereby unrelated organisms evolve similar adaptations in response to SIMILLAR environmental pressures

Parallel

A process whereby unrelated organisms evolve similar adaptations in response to the SAME environmental pressures

Coevolution

A process whereby an evolutionary change in once species influences the evolution of another species

Describe allopatric speciation

Allopatric speciation occurs when a species separates due to physical or geographical isolation

Describe parapatric speciation

Parapatric speciation occurs when populations are separated by extreme change in habitat; populations may interbreed in bordering areas. Species develop their own genetic characteristics that are passed onto offspring

Describe sympatric speciation

Sympatric speciation occurs without geographical or physical isolation. A new species can be formed based on different food source or a reproductive barrier

Understand that different mechanisms of isolation – geographic (including environmental disasters, habitat fragmentation), reproductive, spatial, and temporal – influence gene flow

Gene flow is the transfer of genetic material from one population to another.

Mechanisms of isolation

· Geographic: individuals are separated by geographical features such as seas, mountains, environmental disasters, and habitat fragmentation

· Reproductive: the separation of populations that are unable to interbreed because of changes that produce physical, biological, or behavioural barriers such as different mating calls

· Temporal: individuals breed during different seasons of the year or times of the day

· Spatial: individuals breed in different spaces or are separated by space with no specific geographic barriers

Explain how populations with reduced genetic diversity (those affected by bottlenecks) face an increased risk of extinction

Large populations can be more resilient than smaller populations, because the population has a more diverse gene pool (it holds a greater reserve of different alleles) to draw on as the pressures from a natural selection change. When only a small number of individuals survive a major catastrophic event or quickly changing environmental conditions such as a bottleneck, the surviving population is unlikely to carry all the alleles that were present in the original population. Therefore populations with reduced genetic diversity are more likely to face extinction during a bottleneck.