Diversity of Organisms and Karyotyping (SL) Flashcards
Organism
Any biological system that functions as an individual life form
Population
A group of organisms of the same species in the same area; variation between individual organisms of the population
Community
Populations of two or more different species occupying the same area at the same time; great variation between different species
Variation
Defining feature of life; differences between members of a group
Discrete variation
Traits that can be put into distinct qualitative categories; influenced by one or few genes; can be influenced by environment
Continuous variation
Traits that vary along a quantitative continuum; most types of biological variation; caused by complex interaction between several genes (polygenic); phenotype expression influenced significantly by environment
Variation between species
Amount of variation between individual organisms depends on how closely related they are to each other
Binomial nomenclature benefits
- Reflects evolutionary relationships between organisms
- Enables scientists to talk to each other in the same language
Biological species concept
A species is a group of organisms that can breed and produce fertile offspring
Over 30 definitions of species; has limitations (tiger and lion)
Limitations of the biological species concept
- Asexual organisms
- Hybrids
- Geographically inaccessible locations
- Extinct populations
- Chronospecies (entire species evolving over time)
- Divergence during speciation (gray area)
Divergence during speciation
Populations of the same species who do not interbreed build up genetic differences over time that can cause divergence to the point of becoming separate species
Makes distinguishing between different populations and species difficult
Human and chimpanzee chromosomes
Humans: 46
Chimpanzees: 48
Chromosomes
A distinguishing characteristic of a species
Different numbers of chromosomes mean that species cannot mix
Even number of chromosomes in a diploid cell
One set from mother, one set from father
Karyotyping and karyograms
Looking at/arranging by the size and number of chromosomes
Karyotyping process
- Cells are harvested
- Cell division is induced and then chemically stopped (usually during metaphase)
- Chromosomes are arranged into pairs according to size
- Sex chromosomes are shown last
Karyotyping purpose
- Determine the gender of an unborn child using sex chromosomes
- Test for chromosomal abnormalities
*Not the same as looking for genetic diseases
Classifying chromosomes
- Banding pattern created by stains (G-bands)
- Length
- Centromere position
*Banding does not represent genes/specific traits
Human chromosome 2
Thought to have arisen from a fusion of chromosomes 12 and 13 in ancestor (chimps); evidence is similar banding patterns and centromere position
Genome
All the genetic information of an organism
Single-nucleotide polymorphisms
Variations in genomes of organisms of the same species
Genomes vary in…
- Overall size (determined by total amount of DNA)
- Base sequence (including length of chromosome)
Variation between species is much larger than variation within a species
Genome size
Can be measured in terms of number of base pairs or mass of DNA in the nucleus
Larger ≠ more complex
Current and potential future uses of whole genome sequencing
Current: research into evolutionary relationships
Future: personalized medicine
Speciation
Divergence into new species from a pre-existing species
Happens gradually rather than abruptly
