Diversity of Organisms (DP IB Biology)
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Define variation in biology.
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Define variation in biology.
Variation refers to the differences that exist between organisms, such as in visual appearance, behaviour, or biochemistry.
What are the two main causes of variation?
The two main causes of variation are genetic factors and environmental factors.
How is genetic variation generated?
Genetic variation is generated when mutations occur and when alleles are combined in different ways during sexual reproduction.
True or False?
Members of the same species are genetically identical.
False.
While members of a species have a similar genetic makeup, different individuals have different combinations of alleles.
What is discontinuous variation?
Discontinuous variation is when characteristics fall into distinct categories, such as black fur vs brown fur, or human blood type.
What is continuous variation?
Continuous variation means that characteristics can be measured incrementally on a scale, e.g. height.
Define taxonomy.
Taxonomy is the science of classification, and scientists working in this field are called taxonomists.
Who is considered the 'father of taxonomy' and why?
Carl Linnaeus is considered the 'father of taxonomy' because he developed the method of naming species that is used by scientists worldwide today.
What is the binomial system of nomenclature?
The binomial system of nomenclature is the biological system of naming species using a two-part Latin name, consisting of the genus and species name.
How should binomial names be written when typed?
When typed, binomial names should appear in italics, e.g. Patella vulgata.
State the biological species concept.
The biological species concept states that a species is a group of organisms that can interbreed to produce fertile offspring.
What is a limitation of the biological species concept?
Limitations might include:
The species concept cannot be applied to organisms that reproduce asexually, such as bacteria.
Hybrid 'species' can be fertile on rare occasions.
Extinct organisms are not able to breed.
Define speciation.
Speciation is the process by which one species gives rise to two or more new species.
How can isolation lead to speciation?
Isolation can lead to speciation when a population becomes separated from other populations of the same species, preventing gene flow and allowing natural selection or genetic drift to act differently on each population.
True or False?
Speciation occurs rapidly.
False.
Speciation occurs over very long time periods, with differences between isolated populations accumulating incrementally.
What is a diploid cell?
A diploid cell is a cell that contains two complete sets of chromosomes (2n).
What is the relationship between diploid and haploid chromosome numbers?
The haploid chromosome number is half the diploid number, and is equal to the number of chromosome pairs in a diploid cell.
True or False?
The diploid chromosome number can be an odd number.
False.
The diploid number must always be an even number, as it must be divisible by two to produce a whole haploid number.
How does chromosome number relate to different species?
The number of chromosomes possessed by different species varies and is dependent upon changes that have occurred during that species' evolution.
What is the chromosome number of humans?
The chromosome number of humans is 46.
What is the chromosome number of chimpanzees?
The chromosome number of chimpanzees is 48.
Is the number of chromosomes linked to how 'advanced' a species is evolutionarily?
No, the number of chromosomes a species possesses is not linked to how 'advanced' a species is in evolutionary terms.
What is the name given to an image like the one below?
The image shows a karyogram.
What is a karyogram?
A karyogram is an image that shows all of the chromosomes in a cell, arranged by size, shape, and banding pattern, and placed with their homologous pairs.
Define the term karyotype.
A karyotype is the appearance of a complete set of an individual's chromosomes, including their number, size, shape, and banding.
True or False?
Metacentric chromosomes have their centromere located near the end.
False.
Metacentric chromosomes have their centromere located roughly in the middle.
What is an acrocentric chromosome?
An acrocentric chromosome is a chromosome with the centromere near the end and arms of unequal length.
How is a karyogram produced?
Karyograms are made using the following process:
Cells are stained and viewed under a light microscope
Photographs are taken of the contents of the nucleus during metaphase of cell division
The photographs of the chromosomes are cut up and arranged by size, shape, and banding pattern
In humans, how did the chromosome 2 pair evolve?
Chromosomes in pairs 12 and 13 in a common ancestor fused to form the chromosomes in human pair 2.
State two pieces of evidence supporting the hypothesis of how chromosome 2 in humans evolved.
Some examples of evidence for the formation of human chromosome 2 pair are:
Chimpanzee chromosomes 12 and 13 match the length of human chromosome 2
The location of the centromere of chimpanzee chromosome 12 matches that of human chromosome 2
Human chromosome 2 contains a region of non-coding DNA known as satellite DNA that corresponds to the location of the centromere in chimpanzee chromosome 13
The banding of the long arms of acrocentric chimpanzee chromosomes 12 and 13 corresponds to the banding of metacentric human chromosome 2
Human chromosome 2 contains telomeric DNA in the middle of the chromosome
What is telomeric DNA?
Telomeric DNA is a region of DNA found at the ends of chromosomes.
State the meaning of satellite DNA.
Satellite DNA is a region of non-coding DNA that can correspond to the location of a centromere.
What is a testable hypothesis? (NOS)
A testable hypothesis is a statement that can be accepted or rejected based on available evidence and does not contain vague terms, predictions, or causal conclusions.
True or False?
"The fusion of ancestral chromosomes may have reduced the chromosome number" is an example of a testable hypothesis. (NOS)
False.
Testable hypotheses should not contain vague statements that use terms like 'may' or 'could'.
What is the biological sex of the individual shown in the karyogram below?
This karyogram shows a male, as determined by the Y chromosome in homologous pair number 23.
What is a genome?
A genome is all of the genetic information in an organism.
Define the term SNP.
SNP is an abbreviation for single nucleotide polymorphism, which is a difference in a single nucleotide between DNA sequences.
True or False?
Humans share 100% of their DNA with other humans.
False.
Humans share around 99.9% of their DNA with other humans.
What does DNA sequencing mean?
DNA sequencing means determining the entire base sequence of the genes within an organism's genome.
True or False?
Eukaryotic genomes can vary in size.
True.
Eukaryotic genomes can vary in size, which is determined by the mass of DNA present in a nucleus.
State the meaning of mitochondrial DNA.
Mitochondrial DNA is genetic material found in mitochondria, which is included in the genome of eukaryotic cells.
What is plasmid DNA?
Plasmid DNA is genetic material found in small circular DNA molecules separate from chromosomal DNA in prokaryotic cells, which is included in the prokaryotic genome.
What source could be used to find information about genome size of different taxonomic groups?
Databases such as GenBank and NCBI could be used to find information about genome size of different taxonomic groups.
True or False?
Prokaryotes tend to have larger genomes than eukaryotes.
False.
Prokaryotes tend to have smaller genomes than eukaryotes.
What does Mb stand for in genome size measurement?
Mb stands for megabases, where 1 Mb = 106 bases.
True or False?
Similar types of species have similar sized genomes.
False.
In some cases similar species may have very different genome sizes.
E.g. common wheat above has a genome size of around 17 000 Mb, while red wild einkorn wheat has a genome size of around 5 000 Mb.
What is genome sequencing?
Genome sequencing is the process of identifying and recording the base sequence of an organism's genome.
What is the Human Genome Project?
The Human Genome Project was a project that involved sequencing the entire human genome.
Define the term genomic medicine.
Genomic medicine is the use of information about genes to design medical treatments.
True or False?
Genetic screening can help identify individuals with a high chance of developing specific diseases.
True.
Genetic screening can identify individuals with a high chance of developing specific diseases.
How can genome sequencing contribute to personalised medicine?
Genome sequencing can contribute to personalised medicine by allowing doctors to select treatments based on an individual's genotype and identify genetic risks for certain diseases.
What is phylogenetics?
Phylogenetics is the classification of species based on their evolutionary origins and relationships.
What is a phylogenetic tree?
A phylogenetic tree is a diagram that shows the evolutionary relationships between species based on sequence analysis and comparison.
True or False?
DNA sequence data is the only type used to investigate evolutionary relationships.
False.
DNA, mRNA, and amino acid sequence data are all used to investigate evolutionary relationships.