Classification Flashcards
Animals
- multicellular (cells 20-40μm)
- no chloroplasts or cell wall
- heterotrophic
- store carbs as glycogen (broken down fast; high rate of metabolic reactions)
- nervous co-ordination - able to move
- e.g. mammals, insects
Plants
- multicellular
- contain chloroplasts and a cellulose cell wall
- autotrophic
- store carbs as starch or sucrose
- e.g. cereals, legumes
Fungi
- uni/multicellular
- no chloroplasts, chiton cell wall
- heterotrophic (saprotrophic)
- store carbs as glycogen
- mycelium made of thread-like hyphae contenting many nuclei
- can be pathogenic
- e.g. Mucor, yeast
Protoctista
- unicellular
- all have a cell membrane, cytoplasm and a nucleus
- hetero/autotrophic
- e.g. Plasmodium (malaria)
Bacteria
- unicellular
- murein cell wall, cell membrane and cytoplasm
- no nucleus; circular chromosome of DNA and many plasmids
- some have capsule or slime layer
- some have flagella
- most hetero, some autotrophic
- much smaller
- e.g. Lactobacillus, Pneumococcus
Murein
Polysaccharides and proteins
Plasmid
Circular loop of DNA
Viruses
- genetic material surrounded by a protein coat
- some have an envelope
- parasitic
- different types infect organisms across the kingdoms
- wide variety of shapes and sizes
- e.g. tobacco mosaic virus, influenza
Classification
The organisation of living organisms into groups
Artificial classification
- groups organisms for convenience
- based on observable characteristics
- e.g. habitats, movement, colour, size
Natural classification
- groups organisms according to their phylogeny
* based on information from molecular internal biology and external features
Phylogeny
- φυλος γίγνομαι
* evolutionary relationships
Phylogenetic classification system
- arrangés species into taxa based on evolutionary origins and relationships
- arranged in taxa
Taxa
- a series of groups arranged into a hierarchy
- éach taxon contains diagnostic characteristics which indicate that they have common ancestry
- there is no overlap between taxa
Taxonomy
The study of the classification of living things
The taxa hierarchy
Domain Kingdom Phylum Class Order Family Genus Species
Hierarchy
Each taxon is a subset of the one higher than itself; taxa become more exclusive as you go down, and there is no overlap
Domains
- eukarya
- archaea
- bacteria
Kingdoms
- animalia
- plantae
- fungi
- protoctista
- prokaryotae
Phylum
- does the organism have a backbone?
* e.g. chordata
Class
• a group of organisms that all possess the same general traits • overall variation is still quite big • e.g. spiders (Arachnida) • e.g. fruit fly (insecta) -> different no of legs
Genus
A group of similar species with a relatively recent common ancestor
Species
- organisms that can breed together to produce live, fertile offspring
- when a species reproduces sexually, any of its genes can be combined with any other
- all members of a species will show some variation (due to genetic and environmental factors), but are all essentially the same
Phylogenetic group
A group of organisms with a common ancestor
Phylogenetics is dependent on…
… the recent of common ancestors
Grouped by cladistics
Closer branches = more recent ÇA
Clade
A group of organisms with a hypothetical ancestor that share a derived trait
Derived trait
A new characteristic shared only by a group and its hypothetical common ancestor (evolved, causes genetic drift)
Cladogram
- an evolutionary tree that depicts hypothesised evolutionary relationships between organisms
- constructed for competing hypotheses
- depict parsimony
- can show deevolution
- can have outgroups
Parsimony
the simplest possible hypothesis that can explain the observations
Outgroup
- does not have any of the observable traits
- largest number of genetic differences
- common ancestor is the most distant
Binomial nomenclature
- devised by Carl Linnaeus
- ‘two names’: generic, specific
- written: Generic specific
- universal
- based upon Latin and Ancient Greek
- if the species name is unknown, written as sp.
Morphology
- previous classification technique
- anatomy and bone structure
- visual characteristics: size, height
- massively flawed!
Why is morphology flawed?
- some visual characteristics are polygenic
- some changes may be too discreet to notice
- some changes may be environmental, not due to changes in alleles
- there are also massive fluctuations in visual characteristics within a species
Polygenic
Controlled by many genes
Modern methods of classification
1) genetic comparisons
2) protein comparisons
3) immunological comparison
4) courtship behaviours
(Occasionally use biological molecules such as RNA polymerase)
Genetic comparisons basics
- can be done using DNA or mRNA (no introns)
- DNA is extracted, base sequence read to determine similarity
- less related species less similar- natural selection causes DNA base sequence to change (accumulation of mutations over time)
- to be read, each nucleotide is tagged with a different fluorescent dye
- only coding DNA is used in analysis, because introns vary massively within species’
Fluorescent dyes used in genetic comparisons
- A = green
- T = red
- C = blue
- G = yellow
Genetic comparisons in the lab
1) extract DNA from 2 species and remove introns
2) heat to break hydrogen bonds; separates strands
3) mix 2 species in 1 tube, keep 1 tube separate
4) cool
5) warm slowly
6) measure amount of single-stranded DNA every 2°C
7) determine temperature at which 50% of DNA has separated into single strands (T50H)
8) measures difference between 2 temperatures at T50H
9) 1°C difference = 1% difference in base sequence
Why cool during genetic comparison in the lab
- allows base pair formation between strands
* DNA with complementary sequences base pair; mismatched sequences do not
DNA hybridisation
- genome sequencing
- v. Expensive
- v. Slow
- whole genome must be sequenced - only a few genes gives massively flawed evidence
Protein comparisons
- AA sequence; primary structure
- usually uses cytochrome c/ Hb
- species will likely have exactly the same amino acid sequence (could have 1 difference due to mutation of alleles)
- not as accurate or reliable as DNA comparisons due to degenerate nature of DNA; multiple DNA triplets code for the same AA, so the difference in DNA sequence might not be reflected in the amino acid sequence
Immunological comparisons - basics
- antibodies
* often used because there are very few universal proteins, and protein sequences are different
Immunological comparisons - theory
- ‘agglutination’
- bacteria and viruses (pathogens) have antigens, to which B cells have complementary antibodies
- lymphocytes use antibodies to clump pathogens together, making cell invasion a lot harder
- antibodies of one species will reine to specific antigens on proteins (e.g. albumin), in the blood serum of another
Immunological comparisons in the lab
- serum albumin from species A injected into species B
- species B produces antibodies to all of the antigen sites on the albumin from species A
- serum extracted from species B
- serum B mixed with serum C from a third species
- antibodies respond to their corresponding antigens on the albumin in serum C
- a precipitate forms
- precipitate formation increases with number of similar antigens, and therefore species relatedness
- the more similar, the more anti-A antibodies will react
Courting behaviour functions
- essential; helps to achieve the maximum chance of survival
- attract a mate
- ensure a mage is of the right species and sex
- ensures mate is capable of breeding
- synchronises mating
- heightens sexual responsiveness and suppresses other responses (e.g. flight and aggression) - allows close contact and copulation
- brings a member of the opposite sex into a physiological state that allows breeding to occur
- establishes a pair bond
What determines capability of breeding?
Both partners must be sexually mature, fertile and receptive
What is mating synchronising?
Brings partners together when they are more sexually responsive and fertile (during oestrus); maximum probability of sperm and egg meeting
Process of courting behaviours
1) attracting a mate and signalling sexual status (responsiveness and readiness)
2) females use pheromones to attract males and to signal that they are in oestrus and can conceive
