Classification

Question 1

Define organism.

Answer 1

Organism is any biological system that functions as an individual form of life. All organisms are composed of cells.

Question 2

Define population.

Answer 2

A population is a group of organisms of the same species in the same area.

Question 3

Define community.

Answer 3

Communities are the populations of two or more different species occupying the same geographical area at the same time.

Question 4

Define variation.

Answer 4

Variation is a defining feature of life. Variation reffers to differences between members of a group, they can be continous or discrite.

Question 5

Explain discrite variation.

Answer 5

Traits that can be put into distinct qualitative categories. Usually influenced only by one or a few genes, eg. blood type, being left or right handed.

Question 6

Explain continous variation.

Answer 6

Traits exhibit a range of values without distinct categories. Result from complex interaction between many different genes, often with the environment playing a significant part, eg. height, root length in a plant.

Question 7

List sources of genetic variation within a species.

Answer 7

Variation within the species is called “intraspecies variation” and is heritable.
Genetic variation within a species can result from:
- mutation - changes in DNA sequence
- meiosis - formation of egg and sperm which leads to creations of new combinations of alleles
- sexual reproduction - random fertilisation between egg and sperm

Question 8

Compare variation within and between species.

Answer 8

Variation within the species enables some organisims to survive better than others in the environment in which they live. As a result, these organisms are more likely to reproduce and pass on their beneficial variation.

Variation between the species - the amount of variation between individual organisms depends on how closely they are related to each other.

Question 9

Define species.

Answer 9

A species is a group of organisms that share similar traits, interbreed, and are reproductively isolated.

Question 10

Define binomial nomenclature.

Answer 10

The binomial system of nomenclature is the formal system by which all living species are classified.
The first part of the name identifies the genus, with the second part of the name distinguishing the species. Species in the same genus have similar traits. The genus name is given an initial capital letter but the species name is lowercase.

According to the binomial system of nomenclature, every organism is designated a scientific name with two parts:
* Genus is written first and is capitalised, followed by species in lower case (e.g. Homo sapiens).
* Some species may occasionally have a sub-species designation (e.g. Homo sapiens sapiens – modern man).

Question 11

Outline why the binomial naming system is used in science rather than local names.

Answer 11

It allows for the identification and comparison of organisms based on recognised characteristics

It allows all organisms to be named according to a globally recognised scheme

It can show how closely related organisms are, allowing for the prediction of evolutionary links

It makes it easier to collect, sort and group information about organisms

Question 12

Define species according to the biological species concept.

Answer 12

According to the biological species concept, a species is a group of organisms that can interbreed and produce fertile, viable offspring

Members of a single species are unable to produce fertile offspring with members belonging to a different species

If different species do produce offspring, the infertile progeny are referred to as a hybrid species (e.g. horses and donkeys can produce mules

Question 13

Describe the challanges and limitations with the biological species concept.

Answer 13

Naturally and artificially produced hybrids.
Divergence during separation.
Asexually reproducing organisms.

Question 14

Define a hybrid.

Answer 14

A hybrid is the offspring resulting from sexual reproduction between two closely related but separate species, eg. a mule is a hybrid of horse and donkey.

Question 15

Explain the difficulties in distinguishing between populations and species during speciation.

Answer 15

When two populations that have been diverging come back into contact, the reproductive isolation between them might be incomplete. If it is incomplete hybrids may be produced.

Even when separation has occured, related species can be hard to distinguish between each other. Eg. “Bigg’s” and “resident” orca killer whales are separate species not simply different populations of the same species.

Question 16

State the importance of compatible genetic profiles in inbreeding of species.

Answer 16

In order for members of a species to interbreed, they must have compatible genetic profiles.

The genetic information of each parent must be organised onto the same number of chromosomes, with comparable sizes and gene loci positions.

Organisms with different diploid numbers are unlikely to be able to interbreed as the chromosomes cannot form homologous pairs.

Question 17

Explain chromosome number in distinguishing species.

Answer 17

Chromosome number is a characteristic feature of members of a particular species and can be used to deduce evolutionary relationships.

Question 18

State the number of chromosomes in humans and in chimpanzees.

Answer 18

Humans have 46 chromosomes while chimpanzees have 48 chromosomes – indicating that they are different species.

However, the two species share a common ancestor and it is hypothesised that chromosome 2 in humans arose from the fusion of chromosomes 12 and 13 in the primate ancestor.

Question 19

Evidence for the Fusion of Human Chromosome 2.

Answer 19

1. Banding Pattern Similarities
Human chromosome 2’s banding patterns match those of chimpanzee chromosomes 12 and 13, suggesting a fusion of these two ancestral chromosomes.
2. Telomeric Sequences in the Middle
Telomeres are typically found at chromosome ends.
However, telomeric sequences are present in the center of chromosome 2, consistent with a fusion point.
3. Remnants of a Second Centromere
Chromosome 2 contains evidence of an inactivated centromere, aligning with the position of the centromere on chimpanzee chromosome 12.
The active centromere corresponds to chimpanzee chromosome 13.

Question 20

Define karyotype and karyogram.

Answer 20

Karyotyping is the process of pairing and ordering the complete set of chromosomes within a cell to provide a snapshot of an organism’s genetic profile.

The chromosomes can then be photographed to generate a visual representation called a karyogram.

Question 21

List the characteristics by which chromosomes are paired and arranged on the karyogram.

Answer 21

Chromosomes are classified based on three key criteria: banding patterns, length, and centromere position.

These features provide insights into chromosome organization and variations.

Question 22

Describe the process of classifying chromosomes on a karyogram.

Answer 22

1. Banding Patterns
2. Chromosome Length
Chromosomes are arranged in a karyogram by decreasing size.
Human chromosome 1 is the longest, while chromosome 21 is among the shortest.
3. Centromere Position
Chromosomes are categorized based on the location of the centromere:
* Telocentric: Centromere located on one end
* Acrocentric: Centromere is near one end, creating a very short p arm (e.g., chromosome 21).
* Submetacentric: Centromere is slightly off-center
* Metacentric: Centromere is centrally located

Question 23

What can karyotyping determine?

Answer 23

Karyotyping can be used to determine three key things:
* The type of species (chromosome number is a characteristic feature of a species)
* The sex of the organisms (in humans, males are XY and females are XX)
* The presence of any chromosomal abnormalities (e.g. translocations or aneuploidies)

Question 24

Define autosome and sex chromosome.

Answer 24

Autosomes are the 22 pairs of chromosomes that are identical in both males and females, determining most traits.
Sex chromosomes, the 23rd pair, differ between males and females and are involved in sex determination.

Question 25

Define genome.

Answer 25

Genome is the complete set of genetic instructions that determines the structure, function, and traits of an organism. The genome is the totality of genetic information present in every cell within an organism: * This includes all genes as well as non-coding DNA sequences (introns, promoters, short tandem repeats, etc.) * It also includes all non-nuclear sequences – such as plasmid DNA (in prokaryotes) and organelle DNA (in eukaryotes)

Question 26

Explain variations in alles in genomes.

Answer 26

Organisms in the same species share most of their genome but variations in alleles give some diversity. In most cases, different alleles will only vary from one another by one or only a few bases.

Question 27

Outline the cause and effect of “single-nucleotide polymorphisms” in genomes.

Answer 27

A single nucleotide polymorphism (SNP) is a mutation to a single nucleotide base that is present in a sufficiently large proportion of the population (typically >1%). By identifying all SNPs within the genome, a unique genetic profile can be made for any individual. **Trait Variation:** SNPs contribute to differences in height, fur color, or disease resistance. **Evolutionary Insights:** They act as markers to trace inheritance patterns and evolutionary relationships. **Individual Uniqueness:** SNPs drive the subtle variations that differentiate individuals within a population.

Question 28

Compare variation in genomes sizes and gene sequences within a species.

Answer 28

Genomes vary in both size (total amount of DNA) and organisation (total number of chromosomes) Genomes also vary in base sequence – with variation between species being much larger than variation within a species. Organisms in the same species share most of their genome (same genes), but differences will exist within the base sequence (different alleles) For example, all humans share approximately 99.9% of their genetic makeup, with the differences creating the variation seen in each individual

Question 29

Compare variation in genomes sizes and gene sequences between species.

Answer 29

Genome size can vary greatly between organisms * Viruses and bacteria tend to have very small genomes, while most eukaryotic organisms have larger genomes * Sizes of plant genomes can vary dramatically due to the capacity for plant species to self-fertilise and become polyploid

Question 30

State the relationship between the number of genes in a species and the species complexity in structure.

Answer 30

Due to significant diversity, genome size is not a valid indicator of genetic complexity * Small animals (guinea pigs) and large animals (elephants) can have similar genome sizes * Some animals can have a small genome size but large numbers of chromosomes (and vice versa)

Question 31

Define “sequence” in relation to genes and/or genomes.

Answer 31

Whole genome sequencing is the process of determining the DNA sequence of an organism's entire genome at a single time As almost every cell in the body contains the full complement of the organism’s DNA, even a small amount of biological sample (saliva, hair, etc.) can be used for sequencing

Question 32

List applications of genome sequencing.

Answer 32

The two main applications of whole genome sequencing are to provide genealogical information and identify any mutations that could cause health problems * Genealogical data can be used to determine ancestral relationships and map individual pedigrees * Health data can be used to predict disease predispositions and develop personalised medicines (via pharmacogenomics)

Question 33

Explain the increasing speed and decreasing costs of genome sequencing.

Answer 33

Key factors driving these advancements include: * **High-throughput sequencing:** Platforms like Illumina and PacBio process millions of DNA fragments simultaneously, drastically reducing sequencing time. * **Portable devices:** Tools like the Oxford Nanopore MinION enable sequencing in remote and real-time settings, from clinical labs to fieldwork in rainforests. * **Advances in bioinformatics:** Improved algorithms and software accelerate genome assembly and analysis, simplifying complex data processing.

Question 34

List key contributions of whole genome sequencing to evolutionary studies.

Answer 34

**1. Comparative Genomics:** By aligning DNA sequences, scientists identify: * Conserved regions (shared across species): Highlighting essential genes. * Divergent regions (unique to species): Explaining adaptations. **2. Molecular Clocks** Mutations accumulate at predictable rates, allowing researchers to estimate the time since species diverged from a common ancestor. **3. Horizontal Gene Transfer (HGT)** WGS uncovers instances where genes are transferred between unrelated species, such as antibiotic resistance spreading among bacteria.

Question 35

Discuss ethical considerations of genome sequencing.

Answer 35

**Privacy and Ethics:** How can genetic data be protected from misuse or unauthorized access? Should employers or insurers have access to genetic information? **Equity in Access:** Will WGS benefits be accessible globally, or will they widen healthcare disparities? **Interpreting Complexity:** Many diseases involve gene-environment interactions, making predictions based on WGS alone uncertain.