IB Biology HL/SL: Genetics and Evolution (Unit 3, 5, 10 )

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.