Unit 5: Evolution and Biodiversity

5.3 Classification, 5.4 Cladistics, 1.1 origin of cells, 1.2 cell structure

Binomial System

first name is “Genus”, second name is “species”; italicised. Earliest published name is correct, may be abbreviated to “G. species”.

Classification conventions for eukaryota

Domain → Kingdom → Phylum → class → order → family → genus → species

Eukaryota

One of the three domains: cells with a membrane-bound nucleus

Prokaryota (Eubacteria)

One of the three domains: unicellular without a membrane-bound nucleus. High degrees of organisation. Bacterias.

Prokaryota (Archaea)

One of the three domains: unicellular without a membrane-bound nucleus. Can survive in harsh conditions. Oldest form of life.

Kingdoms

plants, animals, fungi, protocista

Natural Classification

Classified based on evolving from the same ancestor. Advantages:

1. systematic identification of species

2. prediction of characteristics in future

DNA/amino acid sequencing > morphology (physical traits)

Unnatural Classification

based on shared characteristics. However, two genetically unrelated species may share the same trait (eg flight) through Convergent Evolution.

Convergent Evolution

genetically unrelated organisms evolve similar “analogous” structures, traits or habits.

Clade

group of organisms that have evolved from a common ancestor

“Molecular Clocks”

as mutations occur at a relatively consistent rate, the number of mutations can serve as a timer as to when two species diverged.

Homologous traits

similar due to linked ancestry

Analogous traits

similar because of convergent evolution and not ancestry

Cladograms

tree diagram that indicates species in a clade

• principle of parsimony: computer programs map evolution through DNA/Amino acid changes

• Nodes: branching points in diagram

Characteristics of life

MR H. GREN

Metabolism, Response, Homeostasis, Growth, Reproduction, Excretion, Nutrition

Electron microscopes

• scanning: 2d photo

• transmission: 3d video

Cell theory

1. cells only arise from preexisting cells

2. all living things have 1 or more cells

3. cell is the smallest unit of life

Exceptions to cell theory

striated muscle cells, giant algae, aseptate hypha, the first life

Paramecium

Example of life: cell blob

M: enzymes in cytoplasm

R: cilia moves cell

H: contractile vacuoles

G: grows

R: asexual and sexual

E: membrane diffusion

N: ingest and digest

c. elegans

Example of life: worm

M: diffusion and gas exchange

R: moves on touch

H: intestine

G: during larval stage

R: asexual and sexual

E: secretary gland

N: eat bacteria

Abiogenesis

1950s Miller-Urey experiment replicated conditions of early atmosphere with heat and lightning. first lifeforms which arose from the primordial soup were simple organisms that gradually became more complex throughout aeons. Life didn’t just spawn in.

Panspermia Hypothesis

first biomolecules arrived on an asteroid from space.

Ecological locations for life

Hydrothermal vents provide heat and nutrients for first tidal pool life to form.

Magnification

degree to which size of image is larger than og thing eg zoom

Resolution

Degree to which one can distinguish between two very close objects eg pixels

Conversion

metres (x/1000) millimetres (x/1000) micrometers (x/1000) nanometres

image size = actual size x magnification

Cell differentiation

all cells contain all instructions to make any cell. triggered on and off through supercoiling (DNA cant replicate if it is coiled). acetylation uncoils DNA while removing acetyl groups supercoils it around histone proteins.

stem cells

can self replicated, not fully differentiated (embryonic, adult bone marrow). totipotent > pluripotent > multipotent > unipotent

Sources of stem cells (pros and cons)

embryonic

• many stem cells, toti/pluripotent, regulated

• rejection for transplants, embryo destroyed

umbilical cord

• embryo unharmed,

• limited doses, hereditary disorders, storage, slow to graft

adult

• less likely to be rejected for transplants, regulated, differentiation

• rarely pluri/totipotent, harvest from live human

induced pluripotent stem cells

• adult stem cells genetically reprogrammed into embryonic stem cell, unlimited

• very new untested technology

binary fission

cellular division for prokaryotes

prokaryotes vs eukaryotes

prokaryotes: 1x circular DNA, no histones, no organelles, smaller

eukaryotes: linear chromosomes, histone-bound proteins, organelles, bigger

Eukaryotic cell

membrane, nucleus (double membrane), nucleolus, ribosomes, mitochondria, golgi apparatus, vesicles, cytoplasm, rough/smooth endoplasmic reticulum, ribosomes, vacuole, centriole, lysosomes

plants vs animals

plants: cell wall + membrane, chlorophyll + chloroplasts, large vacuole, form a grid in mitosis

animals: cell membrane, no chlorophyll, small vacuole, completely separate in mitosis.

Plant phyla

angiophyta- flowering

coniferophyta- pines/ cones

bryophyta- mosses/ liverworts

filocinophyta- ferns

Animal Phyla

chordata- vertebrates, bilateral symmetry

arthropoda- exoskeletons, many legs

porifera- sponges, no symmetry

annelida- round worms, segments

mollusca- shell, muscle foot, no segments

platyhelminthes- flat worms

cnaidaria- jellyfish, radial symmetry

echinodermata- sea star, invertebrates with spines

Evolution

a change in the frequencies of alleles within a gene pool over time. heritable characteristics = coded for by DNA

Theory of Natural Selection

individuals best adapted to an environment survive to reproduce a greater number of offspring. thus, favourable heritable characteristics are passed on in higher proportion.

variation

caused by mutation, meiosis (crossing over possibilities) and sexual reproduction

overproduction

Producing more offspring than is viable to ensure that all available resources are used- any leftover offspring die off. Fosters competition, variation, probability of survival. [ex: nazca boobies 2 offspring kane and abel]

mutations

silent- no change in amino acids

missense- change in amino acids

nonsense- change in base DNA codes for a stop (partial translation, often fatal)

variations cannot be passed on if acquired during lifetime.

adaptations

physical, physiological, behavioural

linear VS adaptive radiation

change from one trait to another VS multiple variations of a trait from a base one

Process of Natural Selection

1. heritable variation

2. overpopulation

3. selective pressures

4. favourable alleles survive to reproduce

5. over time favourable alleles more common

Evidence for evolution

1. fossils

2. embryology

3. homologous structures

4. artificial selection as a proxy

5. biogeography

6. biochemistry

Stabilising selection

selection gravitates towards one “average” better trait

directional selection

selection moves in one direction favouring one kind of trait

disruptive selection

selection favours two extremes and average is phased out

Process of speciation

natural selection → divergent evolution → speciation → species

Species

organisms that can interbreed to produce viable offspring

hybrid

an infertile mixture between two species