4.2.2: Classification and evolution Flashcards
Classification
Putting living things into groups with other organisms that share similar characteristics.
Number and names of historic taxonomic groups:
7 groups • Kingdom • Phylum • Class • Order • Family • Genus • Species
Current taxonomic groups
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Phylogeny
the study of evolutionary relationships between species.
Traditional classification kingdoms
Prokaryotae, protoctista, plantae, fungi, animalia
3 domains
- Bacteria
- Archaea
- Eukaryotae
Kingdoms of modern classification (x6)
- Eubacteria
- Archaebacteria
- Protoctista
- Plantae
- Fungi
- Animalia
Why scientists classify organisms
- To identify species
- To predict characteristics
- To find evolutionary links
Eubacteria (kingdom)
- Unicelluar
- No nucleus (prokaryotic)
- No membrane-bound organelles
- Carry out respiration on meso
Eubacteria (kingdom)
- Unicelluar
- No nucleus (prokaryotic)
- No membrane-bound organelles
- Carry out respiration on mesosomes
- Smaller ribosomes (70s) than other organisms
Mesosome
Folding in the cell surface membrane
Archaebacteria (kingdom)
- Unicellular, no nucleus or membrane-bound organelles
- Virtually unchanged since they evolved –> ancient
- Can survive in extreme environments e.g. hot thermal vents or acidic/anaerobic conditions
Protoctista (kingdom)
- Eukaryotic
- Mostly single-celled
- Mostly free living (don’t live within other organisms)
- Can be autotrophs or heterotrophs
- Some have chloroplasts
- “Dustbin kingdom”
Plantae (kingdom)
- Multicellular eukaryotes
- Autotrophs (because of photosynthesis)
- Contain chlorophyll
- Cellulose cell wall
- Store glucose as starch
- Can reproduce sexually or asexually (some)
Fungi (kingdom)
- Heterotrophic eukaryotes
- Unicellular (yeast) or multicellular (mushrooms)
- Chitin cell wall
- Reproduce using spores
- Saprophytic (secrete enzymes)
- Store glucose as glycogen
- No chloroplasts
- Consist of a mycelium (network of multinucleate hyphae)
Animalia (kingdom)
- Multicellular eukaryotes
- Heterotrophic
- No cell wall
- Fertilised egg develops into blastula
- Usually able to move
- Store glucose as glycogen
Chordata
Name of phylum; mostly vertebrates
Common ancestor
Organism from which two organisms evolved.
Advantages of phylogenetic classification
✔︎ Produces a continuous tree; scientists are not forced to place organisms into categories they don’t properly fit into
✔︎ Linnean classification implies different groups with the same rank are equivalent; in reality some have much longer histories (compare cats, short, and orchids, long,) and are much more diverse (30 cat species, 20,000 orchid species)
Natural selection
“survival of the fittest”; the best adapted to a given environment survive and reproduce; governed by nature, takes millions of years.
Artificial selection
breeding animals specifically for certain characteristics; governed by humans and takes centuries.
Convergent evolution
some features are so useful that they will develop independently of one another.
Reasons for gaps in the fossil record
- Fossils can be destroyed
- Fossils may not have been discovered
- Fossils are only formed under certain conditions
- Soft bodied organisms may decay before fossils can form
Why are fossils useful?
- Shows how organisms have changed over time (different layer of rock corresponds to different geological era)
- Shows relationships between extinct and extant organisms
Comparative anatomy
• Gives evidence for divergent evolution
⟶ Common ancestor from which different species have evolved, occurs when organisms have adapted to new habitats
How evolution works (Model answer)
1) VARIATION caused by genetic MUTATION
2) Environmental selection of advantageous variations (SELECTION PRESSURE)
3) SURVIVAL OF THE FITTEST
4) Reproduction to pass on advantageous characteristics in the form of ALLELES
5) ADAPTATION: next generation better suited to their environment.
Methods by which bacteria become resistant to antibiotics
- Build protein that forms efflux pump
- Code for antibiotic degrading enzyme
- Code for antibiotic-altering enzyme
Types of variation
- Interspecific (between species)
* Intraspecific (within a species)
Reasons for increased antibiotic resistance
- Failure to finish a course of antibiotics
* Overuse or incorrect use of antibiotics
Two possible causes of variation
- Genotype (genetic causes)
* Environmental factors
Environmental causes of variation (examples)
- Plant height (depends on nutrients/light)
- Hydrangea colour (dependent on pH of soil)
- Human scars (although how the wound heals may be partially genetically determined)
Genetic causes of variation
- Different alleles
- Mutations (change in DNA sequence alters alleles)
- Meiosis (independent assortment m1, crossing over p1, random orientation m2)
- Sexual reproduction (random selection of gametes, combination of alleles from 2 parents)
Genetic causes of variation (examples)
- Natural eye colour
* Blood type
Variation determined by environmental and genetic factors (examples)
- Human height (max. potential = genetic, malnourishment may reduce)
- Skin colour (alleles + sun exposure)
Continuous variation
- No distinct categories
- Tends to be quantitative
- Controlled by genetic factors
- Influenced by environment
Discontinuous/discreet variation
- Distinct categories
- Tends to be qualitative
- Controlled by a few genes
- Unaffected by the environment
Polygenic inheritance
inheritance of a characteristic controlled by many genes which are often located on different chromosomes.
Example of polygenic inheritance
Skin tone; controlled by 8 genes
Standard deviation shows
How much variation there is between the data and the mean. A measure of the spread of the data.
Spearman’s rank correlation coefficient
Determines the strength of a correlation between two variables.
