A3.1 Diversity Of Organisms Flashcards
What is variation between organisms?
- No two individuals are identical in all their traits
- Patterns of variation are complex
- They are the basis for naming and classifying organisms
Why is a classification system important?
To group and organise variation between organisms
Define the term species
A group of similar organisms capable of breeding and producing offspring
What is the original morphological concept?
Individuals of the same species tend to look more similar to each other than to members of other species.
[the classification of organisms into species is based upon this concept]
What is an example of the original morphological concept?
Lions and Tigers:
Two species of large cats closely related but separate species, each with recognisable, distinct characteristics.
What did Linnaeus develop?
The binomial nomenclature— a naming convention for species.
How is the binomial nomenclature used?
Species are named using both their genus and species name:
Genus comes first, first letter is capitalised and identifies the genus
Species name is second, in lowercase and distinguishes the species
What do species in the same genome share?
Common characteristics and similar traits
What do species in the same genome share?
Common characteristics and similar traits
What is sexual dimorphism?
When males and females within the same species have completely different features and appearance
What is the biological species concept and why is it used?
An alternative method for defining species with a basis on ability to interbreed and produce fertile offspring rather than morphology.
Species look too similar too each other or/and sexual dimporphism.
What is an example of the biological species concept?
In species interbreeding, offspring produced will be infertile:
Horse+Donkey=Infertile mule (hybrid)—Mule cannot produce offspring with other mule
HOWEVER some cases mules are fertile so rule is not strict
Why are there competing definitions of what a species is?
Both concepts, binomial (morphological) and biological have limitations ad biological systems are complex so there are competing definitions.
What is an example of diversity in chromosome numbers of plant and animal species (eukaryotes)?
Humans have 46 chromosomes in each diploid cell: 22 pairs of autosomes and 2 sex chromosomes
Chimpanzees have 48 chromosomes in each diploid cell: 23 pairs of autosomes and 2 sex chromososmes
[chimpanzees are our closest living relative, we share 98% of our DNA)
What is speciation?
The formation of new species from the splitting of one pre-existing species into two or more new species.
How does speciation occur?
Gradual long term process after physical splitting of a population.
What is a cause of speciation?
- Reproductive barriers preventing interbreeding between 2 populations
- Physical barriers preventing interbreeding
- Change in behaviour or timing around reproductive cycles
- Occasionally changes in chromosome number resulting in sew species
What is karyotyping?
Determining and analysing the karyotype of an individual
What is the karyotype of an individual?
Banding patterns, length, and centromere position of a chromosome
How is a karyogram done?
Isolating condensed chromosomes taken from actively dividing cells.
Individual chromosomes are stained to highlight banding patterns.
The location of centromere (central region of chromosome pair where two copies of same chromosome stay attached to each other) seen when chromosomes are isolated at the correct point of cell division.
Why do our closest living relatives have different chromosome numbers, what are the 3 pieces of evidence?
We know that speciation events, including changes in chromosome number happen slowly over time.
When a human karyogram is compared to a chimpanzee karyogram we see:
- Genes of chromosome 2 closely match those of the the two suspected fusion chromosomes in chimpanzees
- Telomeric (repetitive sequences that help protect ends of chromosomes from damage) DNA found at fusion region of chromosome 2
- There is a second centromere region (site where cell’s cytoskeleton attaches to chromosome during cell division) that has mutated and does not function
What is the hypothesis for how humans and chimpanzees speciated?
At some point chromosomes 12 and 13 of the chimpanzee karyotype fused, creating chromosome 2 in the human karyotype.
What is the genome?
All of the genetic information of an organism
What is the cause of some diversity in the genome of the same species?
Variation such as SNPs
What are the 2 ways in which genomes differ between species?
Large differences in genome between species due to size and base sequence.
Size of genome: amount of genetic material
Base sequence of genome: determines how DNA is expressed and organisms phenotype
What is genome sequencing?
Process of determining order of the bases in an organisms genetic code
Weaknesses of genome sequencing and current advanced?
Costly, slow process that is becoming more accessible and less expensive thanks to advances in technology.
What are potential future uses of genome sequencing?
Medicine: ability to create personalised medical treatments and interventions based on sequencing of out genome
What are current uses in genome sequencing?
Comparison of genomes for revision of classification system, evolutionary relationships.
What is the reason for interbreeding dot producing fertile offspring? (HL)
Mismatch in chromosome number, unlikely to produce offspring in parent chromosome numbers.
[e.g. mule end up with uneven chromosmes=infertile]
What is a limitation of applying the biological species concept? (HL)
Not applicable to asexually reproducing species or when offspring are genetically identical to parents.
For example, prokaryotes reproduce asexually through binary fission.
Hydra reproduce asexually through budding and offspring are genetically identical to parents.
What is horizontal gene transfer? (HL)
Where genetic material is exchanged between individuals rather than passed on between generations (bacteria)—> has led to huge amounts often of genetic variation between prokaryotes despite asexual reproduction.
What is a dichotomous key and when is it used? (HL)
Tool used to identify species in field experiments. Series of questions based on physical characteristics with only 2 possible answers.
What is DNA barcoding? (HL)
Method of environmental sampling for biodiversity of habitats to be investigated rapidly:
Unknown specimen collected and DNA extracted.
From sample, sequences of DNA identified, creating a unique barcode.
Barcode compared to catalogue of barcodes for identification of species.
