Biology Terminology

Species richness

the number of different species represented in an ecosystem

species evenness

The number of organisms per species represented in an ecosystem.

Predation

The praying of one animal on others

Competition

Interactions between organisms that vie for the same resources

Mutualism

Both organisms benefit (e.g. bee and flower)

Commensualism

One organism benefits and the other is neither harmed nor benefitted (e.g. wildebeest and bird)

Parasitism

One organism benefits whilst the other is harmed (e.g. dog and tick)

Asexual reproduction

A new offspring is produced by a single parent. The new individuals are clones of their parents - genetically and physically identical to each other.

Parthenogenesis

The replication of an egg by mitosis, resulting in diploid cells that are clones of the parent.

Automixis

A version of parthenogenesis where the egg merges with the polar body by-product of meiosis to create offspring that is similar to the mother but not exact clones.

R-strategists

Short lived, high reproduction, quick to mature, little care for their offspring. Unstable conditions results in rapid appearance and removal of individuals and quick, dynamic changes in population.

K-strategists

Longer living, produce fewer offspring, expend a great deal of energy caring for young, longer gestation and longer to reach maturity.

The Domains

Eukarya, Bacteria, Archaea

The Kingdoms

Animals, plants, fungi, protists, eubacteria, archaebacteria

Clade

Within a cladogram, a branch that includes a single common ancestor and all of its descendants.

Common assumptions of cladistics

A common ancestry, bifurcation and physical change

Why are there multiple definitions of species?

Because there are some exceptions/species limitations. Some species can't be defined by their ability to reproduce (asexual reproduction).

Example of a hybrid that doesn't produce fertile offspring

Mule, liger

Intraspecific relationships

Between members of the same species.

Interspecific relationships

Between members of different species.

Levels of habitats in ecosystems

Microhabitat, ecozone and ecoregion.

How does classifying organisms help ecosystem management?

Different ecosystems have certain restrictions and rules for management in place so that the ecosystem can thrive without too much human intervention. In order for ecosystems to be protected, they first have to be classified so the correct restrictions and management plans can be put in place.

Describe stratified sampling (purpose, site selection, choice of surveying technique, bias, methods of data presentation and analysis)

- Used to provide an estimate of species abundance, density and distribution across an ecosystem.
- Quadrats or transect lines are used to measure the species abundance and density.
- The purpose is to determine how abiotic components of an ecosystem effects species abundance and density.
- Random stratified sampling reduces bias and can be done using random number generators to decide which sections of the ecosystem will be sampled. Bias may increase as the sampling distance from a transect line may fluctuate or the calibration of the equipment may be incorrect.
- Data can be displayed in a bar graph or histogram.

NPP = ?

GPP - energy used for metabolism

Percent of energy transferred = ?

(Energy at higher trophic level / Energy at lower trophic level) * 100

Usually around 10% of the energy from one trophic level is transferred to the next trophic level.

Biomass

A measure of the chemical energy that is stored in organic matter, also known as NPP.

Water cycle

Evaporation, condensation, precipitation

Carbon cycle

Introduced into the atmosphere through combustion of fossil fuels. Through photosynthesis, plants convert carbon dioxide into glucose, which contains carbon. Higher trophic levels gain this carbon through consumptions. Respiration re-introduced carbon into the atmosphere through carbon dioxide. Through the death and waste of animals and plants, carbon is transferred to the soil through detritivores and decomposers. Through diffusion, carbon is transferred between the atmosphere and the ocean. Carbon enters the ocean through weathering.

Nitrogen cycle

Atmospheric nitrogen is fixed into the soil through lightning and soil bacteria. Animals consume nitrogen through legumes. Using the ammonia in the waste of animals and the root nodules of legumes, decomposers cause ammonification. Nitrifers convert ammonia ions into nitrites and nitrates through nitrification. Plants and denitrifiers use nitrates and reintroduce them to the atmosphere.

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.

Competitive exclusion principle

If two species share a niche and use the same resources, they will not be able to co-exist at constant population values.

Keystone species

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

Carrying capacity

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

Why is the carrying capacity of a population determined by limiting factors?

Biotic: inter/intraspecies interactions and relationships such as predation, symbiosis, disease and competition.

Abiotic: temperature, wind, light, pH, water/food availability.

Population growth rate = ?

(birth + immigration) - (death + emigration)

Lincoln Index

N = (M*n)/m
N = total population
M = no. Caught, marked and released initially
n = caught second time
m = no. Recaptured

Modes of population growth

Exponential - J-curve
Logistic - S-curve

Ecological succession

It begins with the pioneer community (usually hardy mosses, lichen and grasses). The ecosystem then reaches seres, an intermediate stage where the ecosystem is advancing towards the climax (small shrubs and trees). Finally, the ecosystem reaches a climax community - it is stable, diverse and full of life.

Primary succession

Begins from completely barren environments that have not been previously colonised. E.g. which ice melts near the poles or after a volcanic eruption.

Secondary succession

Occurs after environmental disturbances. As the land has already been colonised, pioneer communities appear more quickly than in primary succession as the soil is already nutrient rich. E.g. after floods and wildfires.

Features of pioneer species

Ability to fixate nitrogen, tolerance to extreme conditions, rapid germination of seeds, ability to photosynthesise

Impacts of human activity

Overexploitation, habitat destruction, monocultures and pollution

Structure of DNA

Double-stranded helix; nucleotides contain deoxyribose (sugar), a phosphate group and a nitrogenous base. The four bases are adenine, thymine, guanine and cytosine.

Explain DNA replication

1. Two strands uncoil and permanently separate from each other. The enzyme helicase is required for separation. Each parent strand functions as a template for the new complementary daughter strand.
2. Synthesis of the new daughter strands is initiated at the replication fork.
3. New nucleotides are added one by one to the end of the growing strand by DNA polymerase.
4. The new strand of DNA is formed in the 5; to 3; direction (this is called the leading strand).
5. In the other strand, DNA synthesis does not occur continuously, but in small fragments (this is the lagging strand).
6. Later, these fragments are joined by the action of DNA ligase enzyme to form a continuous strand (each fragment requires individual primer).

The role of homologous chromosomes in meiosis

Each side of the cell receives one maternal or one paternal copy of each chromosome. Genetic variation is increased by the random assortment of chromosomes.

Crossing over and recombination

Homologous chromosomes are paired and may exchange sections of chromosomes. This allows recombination of DNA, which helps increase the variation between gametes.

Compare and contrast spermatogenesis and oogenesis

Spermatogenesis:
- 4 spermatocytes are produced
- Spermatocytes are continuously produced
- Spermatocytes are produced throughout the male lifespan
- Small, motile spermatocytes are produced

Oogenesis:
- 1 oocyte and 3 polar bodies
- Oocytes are generated before birth and become viable once each month as soon as puberty begins
- Oocyte production ceases when there are no more oocytes (menopause)
- One large, immotile oocyte is produced.

Both:
- Involve the formation of haploid cells by meiosis.

How do independent assortment and random fertilisation alter variations of the genotypes

Law of independent assortment: alleles of 2 or more different genes get sorted into gametes independently of one another. (In other words, the allele a gamete receives for one gene does not influence the allele received for another.)

Random fertilisation: Each sperm is genetically different due to crossing over and independent assortment.

Mutations in DNA replication

Point mutation: occurs when a single base pair is added, deleted or changed. This can include changes in gene expression or alterations in encoded proteins, but most are benign.

Frameshift mutation: the insertion or deletion of nucleotides bases in numbers that are not multiples of three. The entire gene sequence is incorrectly read, meaning the amino acids are added wrong.

Mutations in cell division

Aneuploidy is a chromosomal mutation in which there is one or more extra or fewer chromosomes.

Trisomy is the most common - an extra chromosome.
Monosomy is another kind - a missing chromosome.

How is damage caused by mutagens

UV radiation, ionising radiation (X-rays, gamma rays and alpha particles), heat (breaking of hydrogen bonds) and chemical (base analogues instead of nitrogenous bases that have different properties).

How does non-disjunction lead to aneuploidy

Non-disjunction occurs when homologous chromosomes fail to separate to the opposing poles during meiosis, resulting in cells with gametes that are with the wrong chromosome compliment.

If the error occurred during anaphase I, two gametes will have a lacking chromosome and two will have two copies of the same chromosome.
If the error occurs at anaphase II, there sill be one gamete lacking chromosomes, another gamete that bears two copies of the chromosome, and two normal gametes that each have a copy of the chromosome.

How do inherited mutations alter the variations in the genotype of offspring?

Mutations result from environmental pressures over time and result in new alleles in a population. Mutations that enhance survival will result in a selection advantage. The frequency of particular alleles may vary within a species.

Patterns of inheritance

Autosomal dominant alleles: any non-sex chromosome. If you get the trait from only one parent, you will display the trait.

Sex-linked alleles: a rare way that a trait or disorder can be passed through families. One abnormal gene on the X chromosome can cause a sex-linked dominant trait or disease. These often occur in males due to them having only one X chromosome.

Multiple alleles: multiple alleles may exist in a population level and different individuals in the population may have different pairs of these alleles.
Incomplete dominance: In some cases the phenotype of a heterozygous organism can be a blend between the phenotypes of its homozygous parents. (RR + rr = Rr)
Codominance: where the alleles of a gene pair in a heterozygote are fully expressed. As a result, the phenotype of the offspring is a combination of the phenotype of the parents and the trait is neither dominant nor recessive. (BB + WW = BW)

Polygenetic inheritance

When one characteristics is controlled by two or more genes.
Polygenetic traits exhibit incomplete dominance so the phenotype displayed in offspring is a mixture of the phenotypes displayed in the parents.

Describe the process of making recombinant DNA

Recombinant DNA combines DNA molecules from two or more organisms to create a new molecule of DNA that consists of new genetic combinations.

- Isolation and cutting of DNA
Cells are broken open and organelles are separated to leave pure DNA. Restriction enzymes are able to identify particular sequences of bases and cut the DNA at the required position. They leave 'sticky ends' so the segment can be spliced with a matching 'sticky end' produced when the same restriction enzyme is used to cut the plasmid DNA.

- Insertion of DNA
Plasmids acts as a vector and transfers the cut DNA segment into a prokaryotic cell. DNA ligase can be used to splice the gene into the plasmid, repairing the phosphate-sugar bonds.

- Joining of DNA
DNA ligase joins the DNA together.

- Amplification of recombinant DNA
The plasmid is introduced into the host cell.

Purpose of PCR and gel electrophoresis

PCR is used to produce many copies of a targeted DNA sequence starting from a piece of template DNA. It's purpose is to replicate DNA sequences for analysis.

Gel electrophoresis is used to separate charged molecules such as DNA according to size. The separated molecules can then be analysed against other samples.

Evolution

Change in the genetic composition of a population during successive generations, which may result in the development of new species.

Microevolution

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

Macroevolution

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.

Evolutionary radiation

An increase in taxonomic diversity that is caused by elevated rates of speciation. Usually follows after mass extinction.

Natural selection

The process whereby organisms better adapted to their environment tend to survive and produce more offspring. This process involves reproducing to pass on desirable traits as unfavourable traits die.

Positive selection

A trait is favoured/selected for because it helps ensure the survival of a species.

Negative selection

A trait is not favoured/selected against because it limits the survival of a species.

Phenotypic selection

Stabilising: extreme phenotypes are selected against and the average phenotypes are selected for.

Directional: a single phenotype is selected for and allele frequency shifts in one direction.

Disruptive: extreme phenotypes are selected for and average phenotypes are selected against.

Explain microevolutionary change

Genetic drift: a change in the frequency of an allele in a population due to random sampling.

Gene flow: the movement of genes into or out of a population.

Diversification patterns

Divergent: groups from the same common ancestor evolve and accumulate differences, resulting in the formation of a new species.

Convergent: the independent evolutions of similar features in species of different periods of time.

Parallel: the similar development of a trait in distinct species that are not closely related, but share a similar or original trait in response to similar evolutionary pressure.

Coevolution: two or more species evolve in tandem by exerting selection pressures on each other.

Modes of speciation

Allopatric: when a species separates into two separate groups which are physically isolated from one another, making it impossible for them to breed.

Sympatric: when there are no physical barriers preventing mating and a new species develops spontaneously.

Parapatric: when new species evolve in contiguous, yet spatially separated habitats. Gene exchange does not cease completely.

Bottleneck effect

An extreme example of genetic drift that happens when the size of a population is severely reduced. This can occur from natural disasters that decimate a population, leaving behind a small, random assortment of survivors.

Explain how populations with reduced genetic diversity face and increased risk of extinction.

The more genetically diverse a species is, the more readily they can adapt to changes because they have a greater range of genes and alleles suited for different environments. If this genetic diversity is reduced, then the species are less ready to adapt to changes, increasing the risk of extinction of the species.

Difference between introns and exons

Exons are coding areas whereas introns are non-coding areas of DNA

Telomeres

DNA at the tips of chromosomes. They protect the genome from degradation and unnecessary recombination.