Studied by 6 people
Evolution
The gradual change in a species over time
Speciation
When a species becomes separated and evolve, creating two new species that now cannot interbreed
Which groups of vertebrates have limbs?
Mammals, reptiles, amphibians and birds
What is the pentadactyl limb?
A limb with five digits
Why do so many organisms have a pentadactyl limb?
They must all share a recent common ancestor
What is adaptive radiation?
The evolution of many diverse species from a common ancestor
What is a homologous structure?
Structures that have adapted from the same common ancestor but are found on different organisms
What is selective breeding?
When animals with the desired characteristics are forced to interbreed, to produce an animal with the desired characteristics
Evidence for evolution
Fossils, homologous structures, embryology, geographical
How do fossils prove evolution?
They show species that no longer exist, and no fossils can be found of species that exist today
Melanistic
Dark varieties of typically light coloured insects
An example of melanism evolution
Biston betalarna (peppered moth)
What happened to the peppered moth?
In unpolluted areas, the peppered moths were well camouflaged against the white lichen, but in more polluted areas, the black ones were more camouflaged. The peppered ones were killed off as the industrial revolution came
Mutation
A random error in gene replication that leads to a change
Sources of variation
Mutation, meiosis and sexual reproduction
How does meiosis cause variation?
The random orientation of bivalents and crossing over means that the alleles are all jumbled up
What happens to acquired characteristics?
They do not get passed on to the offspring
Where did Darwin do his investigation?
The Galapagos islands
What organism did Darwin study?
Finches
What was Darwin's book called?
The Origin of Species
Why did beak size need to change?
In the wet seasons, more hard seeds are grown, and larger beaks are needed to crack them open
What is another example of evolution?
Antibiotic resistant bacteria
Binomial name
Genus and then species
What is a dichotomous key?
Asking questions with a yes or no answer to determine what species you have
Hierarchy of taxa
Kingdom, Phylum, Class, Order, Family, Genus, Species
What is classification?
Putting organisms into groups
Artificial classification
A classification based on appearance
Natural classification
A classification based on common ancestors
What are the three domains?
Bacteria, archaeans and eukaryotes
How was it determined that there are three domains?
By looking at ribosomal RNA, which is found in all organisms
Porifera
Sponges
Porifera characteristics
No clear symmetry, Attached to a surface, Pores through the body, No mouth or anus
Cnidaria
Jellyfish, coral
Cnidaria characteristics
Radial symmetry, Tentacles, Stinging cells, Mouth but no anus
Platyhelminths
Flatworms and flukes
Platyhelminths characteristics
Bilaterally symmetrical, Flat bodies, Unsegmented, Mouth but no anus
Annelida
Segmented worms
Annelida characteristics
Bilaterally symmetrical, Bristles often present, Segmented, Mouth and anus
Arthropoda
Insects
Arthropoda characteristics
Bilaterally symmetrical, Exoskeleton, Segmented, Jointed appendages
Mollusca
Snails, clams, squids, octopuses: have a soft body that in many species is protected by a hard shell
Mollusca characteristics
Muscular foot and mantle, Shell usually present, Segmentation not visible, Mouth and anus
Chordata
Vertebrates
Chordata characteristics
Notochord, Dorsal nerve chord, Pharyngeal gill slits, Post anal tail
List some phyla
Porifera, Cnidaria, Platyhelminths, Annelida, Arthropoda, Mollusca, Chordata
Characteristics of fish
Scales, Gills with a single gill slit, Fins supported by rays, Swim bladder for buoyancy, External fertilisation
Characteristics of amphibians
Soft moist permeable skin, Lungs with small internal folds, External fertilisation in water, Protective gel around eggs, Larval stage lives in water
Characteristics of reptiles
Dry scaly impermeable skin, Lungs with extensive folding, Internal fertilisation, Soft shells around eggs, One type of teeth
Characteristics of birds
Feathers, Lungs with parabronchial tubes, Wings instead of front legs, Hard shells around the eggs, Beak but no teeth
Characteristics of mammals
Hair, Lungs with alveoli, Give birth to live young, Mammary glands secret milk, Teeth of different types
Bryophytes (mosses) roots, stems and leaves
Simple leaves and stems, no vascular tissue
Bryophytes (mosses) reproductive structures
Spores produced in a capsule, capsule develops at the end of a stalk
Filicinophytes (ferns) roots, stem and leaves
Non-woody stems, leaves curled up in bud and often divided into pairs of leaflets (pinnate), vascular tissue
Pinnate
A leaf vein pattern that looks like a feather. There is one main vein that has smaller veins branching off sideways from it
Filicinophytes (ferns) reproductive
Spores produced in sporangia, usually on the underside of the leaves
Coniferophytes (conifers) roots, stems and leaves
Have roots, woody stems, narrow leaves with thick waxy cuticle, vascular tissue
Coniferophytes (conifers) reproductive
Seeds which develop from ovules on the surface of female cones, male cones produce pollen
Angiospermophytes (flowering plants) roots, stems and leaves
Stems of shrubs and trees are woody, vascular tissue
Angiospermophytes (flowering plants) reproductive
Seeds which develop from ovules inside ovaries in flowers, fruits
Wha is a clade?
A group of organisms that evolved from one common ancestor
Homologous characteristic
Similar in two or more species because they are inherited from a common ancestor
Convergent evolution
Process by which unrelated organisms independently evolve similarities when adapting to similar environments
How can clades be identified?
By looking at the base sequence of a gene
Why can anatomical features not be used to identify a clade?
Because some species have analogous characteristics
Cladogram
Diagram that shows the evolutionary relationships among a group of organisms
What is a node?
A branch showing a common ancestor
Cladistics
The method of classifying organisms using clades
Analogous characteristic
Performing a similar function but having a different evolutionary origin, such as the wings of insects and birds.
DNA Molecule
comprised of a pair of antiparallel strands with linear sequences of nucleotides
Gene
A particular section of DNA that can be transcribed and translated to form a specific polypeptide. Is an inheritable factor that controls a specific characteristic.
Allele
A slightly different form of a gene. Slightly diferent base sequences between allels of one gene
Codon
a triplet of nucleotides within an mRNA molecule
Base Substitution Mutation
The incorrect insertion of a nucleotide, the incorrect sequence is then translated and transcribed
Locus
The location of a gene on a chronosome
Genome
All the genetic information of an organism
Human Genome Project
mapped all the genes in the human body located specific genes helps analyse evolutionary relationships discovery of proteins and function **morals
Sickle Cell Anemia
base substitution mutation recessive carriers cannot have malaria
GAG is the normal codon GTG in sickle cell patients
transcribed to GTG instead of normal GAG. GTG forms valine (amino acid) normal is glutamic acid --> this results in a change in the sequence of the hemoglobin protein
cells are sickle shape, don't carry oxygen well, clog veins more, person is more tired.
Genome size
the total amount of DNA the total number of nuclotide base pairs within one cope of a single genome. complexity is not proportional to size NOT the number of genes
Gene number examples
Homo Sapiens - 23,000 genes Ecoli - 3,000 genes thaliana plant - 25,000 genes
Chromosomes
Are made up of lengths of DNA They carry the organism's genetic information
Prokaryotic DNA
circular chromosomes
free in the cytoplasm, not compartmentalised
extra genetic material in plasmids
cell has only 1 chromosome
no histone proteins holding the chromosomes
Eukaryotic DNA
Chromosomes are wrapped around 8 histones and sealed with the 9th
2+ chromosomes
Sealed form the rest of the cell in the nucleus by a double membrane
no plasmids
Linear chromosomes
Interphase
Eukaryotic chromosomes coil then replicate so that after the first division both daughter cells will be diploid.
Somatic Cell
A normal body cell. Not a sex/gamete cell
Gamete
sex cell (sperm or egg)
Homologous Chromosomes
Chromosomes carrying the same genes at the same locus, but not the same allels
Karyogram
A chart of all the homologous chromosome pairs in the organism, ordered by decreasing size.
Karyotype
The number and type of chromosomes in the nucleus
Sex Chromosomes
X and Y chromosomes. Determine the sex of an organism
Haploid and Diploid
Diploid:
has homologous pairs of sister chromatids joined at the centromere
Haploid:
has one set of chromosomes, sister chromosomes joined at the centromere.
Once split, these sister chromatids are considered chromosomes
Genome size comparison
T2 Phage (virus) - 3569 (first RNA genome sequence) E.coli - 4.6 x 10^6 fruit fly - 130 x 10^6 human - 3200 x 10^6 Japanese pale petal - 150,000 x 10^6 (largest known of plants)
Meiosis
A reduction division of one diploid nucleus to form four haploid nuclei. Allows for a full nuclei of chromosomes after fertilization
Meiosis stages (SL)
Interphase: chromosomes are replicated
Prophase 1
chromosomes supercoil, homologous pairs line up, crossing over takes place, microtubules form, nuclear envelope breaks down
Metaphase 1
Homologous pairs line up along the equator, microtubules attach to centromeres, random alignment of maternal/paternal chromosomes to increase genetic variety
Anaphase 1
microtubules contract towards either end of the cell, sister chromatids remain together, homologous pairs are separated
Telophase 1
Spindle fibers break down new nuclear envelopes form around each new group of chromosomes
Cytokenisis
The cell pinches together and separates the two cells
Prophase 2
New spindlefibres form by replication, chromosomes recoil, nuclear envelope begins to break down
Metaphase 2
nuclear envelope finishes breaking down, chromosomes line up along the equator, spindle fibres attach to the contromeres.
Anaphase 2
Spindlefibres contract to wards either end of the cell, separating the sister chromatids, spindle fibres pull the sister chromotides to opposite sides of the cell
Telophase 2
new nuclear envelopes form around the separated chromatids, chromosomes uncoil
Cytokenisis: cell pinches and divides into 4 haploid cells.
Genetic variation comes from…
fertilisation, crossing over, random orientation, mutation
Non-disjunction
When sister chromatids or homologous pair have not separated properly.
More common in elderly parents. Prenatal screening can be important in locating this.
Genotype
An organism's alleles represented by a letter. The come in pairs (one from each chromosome
Phenotype
The characteristics of an organism, external or internal. Eg. Colour, hair, sickle cell anaemia
Dominant allele
The allele that shows whether homozygous or heterozygous. Has a capital letter.
Recessive allele
The allele that only has an effect when it is homozygous. Has a lower case letter
Codominant allele
Pairs of alleles that both effect the phenotype in a heterozygous state. Eg. White and red = pink.
Note 
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