Evolution Chapter 25 and chapter 22

Abiotic synthesis

Organic molecules formed spontaneously and accumulated into a prebiotic soup.

prebiotic soup hypothesis

in atmosphere near volcanoes during an eruption (miller urey experiemnt)

Iron sulfur hypothesis

in deep sea thermal vents, after oceans formed

How early cells were formed (lipids)

Lipids such as phospholipids assemble spontaneously into bilayers thus creating an enclosed space

Pre cells or protocells:

particles made of polymer of organic molecules surrounded by a phospholipid membrane were able to divide by binary fission, maintained homeostasis and exhibited catalytic activity.

Why did protocells use RNA

RNA is single stranded and can take on many shapes, unlike dna. This explains why some rna molecules can self replicate and some have catabolic activities including peptide bond formation. 

Heterotrophs

relies on others to obtain food and energy, usualky aerobic

Autotrophs

Producers, depend on light and inorganic CHNOPS for synthesizing their macromolecules. phtosynthesis, green organisms

faculative meaning

can live in both aerobic and anerobic conditions

obligate strict:

cannot grow in the presence of o2 or abscense of o2

first cell

prokaryotic bacteria (LUCA)

prokaryotic anaerobic heterotrophs (3.5B ago): what they ate and their evidence

organic molecules from prebiotic soup. 

known from fossilised stromalites: colonies of bacteria (like rock formations)

How photo-autotrophs came (3B ago)

once prebiotic soup materials became scarce, some became able to turn CO2 into organic compounds with light energy. (produced O2)

first water splitting photosynthetic prokaryotes

cyanobacterial ancestors were the first water splitting photosynthetic prokaryotes

explain oxygen revolution (2.5B ago)

o2 started to accumulate after all metal oxidised, so first aerobic heterotrophs evolve.

endosymbiont theory - origin of eukaryotes (2B ago)

1) Ancestral anaerobic heterotrophs with characteristics of eukaryotes engulfed by phagocytosis an ancestral aerobic prokaryote — > an endosymbiotic relationship established when an aerobic eukaryotic host cell—> the prokaryote became a mitochondrion

first true aerobic eukaryotic heterotroph

2) a second endosymbiotic relationship established when an aerobic eukaryote engulfed an ancestral cyanobacterium —> cyanobacterium became a chloroplast

first plant like photoautotroph.

Evidence for the endosymbiotic theory

1. chloroplasts and mitochondria have inner and outer membranes. inner like plasma membranes of prokaryotes. outer membranes evolved from the phagocytosed host plasma membrane

2. chloroplasts and mitochondria have circular chromosome and divide by bonary fission similar to prokaryotes !!***

3. chloroplasts and mitochondria produce parts of their transcription and translation machineries

4. chloroplast and mitochondrial ribosomes are very similar to prokaryotic ribosomes.

Multicellularity (how multicellular organisms came)

• eukaryotic cells are larger and more flexible because of cytoskeleton (microfilament and tubules). 

• can form cell-cell interactions through protein complexes on their membranes.

  • only through eukaryotic cell interactions could the first multicellular organisms with specialised cells, tissues and organs evolve about 1 billion years ago. these earliest eukaryotes were protists, some unicellular and some multicellular.

How could the colonisation of land happen

• Ozone layer: Protect UV mutations

• Diploid chromosomes: less chance of mutations

adaptive radiation

divergence of species from one ancestor species. they emerge together with different adaptations

what enables adaptive radiation (4)

1. Multicellularity

2. colonisation of land enables new niches (water to land, new islands, etc)

3. Mass extinctions (75% in 1-10 million years)

Example: dinosaur extinction enables mammal radiation

4. Plate tectonics - continental drift (marsupials after Australia movement)

defintions on page 8 ( didnt feel was encessary)

Species types and their definitions (4)

• Morphological species: organisms that have similar structure

• Biological species: members of a population that interbreed and produce fertile offspring

• Ecological species: same ecological niche

• Phylogenetic species: share common ancestry based on DNA sequences

Evoluntionary theories

1. Creationism: all species are fixed and immutable (catastrophism to explain fossilisation with mass extinction)

2. Inheritance of acquired characteristics: organisms pass on adaptive traits in their lifetime (eg organ dies so son won’t have organism)

3. Evolutions through natural selection or descent with modification

4. Neodarwinism

Darwins theory influences (4)

• Lyell’s principle of geology: earth evolves slowly and continuously.

• Malthus principles of populations: Populations increase exponentially, food increases linearly.

• Artificial selection

• Voyage around the world

NeoDarwinism

• Random mutations: crossing over and independant assortement, random fertilisation

• Mendelian genetics

aspects of natural selection

• Individuals vary (phenotypic expression)

• More offspring than ability to support them (overproduction)

• Struggle for existence (competition for limited resources)

• differential success in survival and reproduction

observation, inference

Mutation characteristics

• random

• pre-adaptive: if useful, will be selected for and vice versa

• Not all mutations are expressed (often recessive and non coding, neutral)

fitness

success in survival and reproduction

Types of natural selection and examples

1. Directional: AA < Aa < aa or aa<Aa<AA

ex: moths industrial melanisation, horses larger and one toe foot, drought causing bigger beaks from lack of small seeds

2. Stabilizing: AA>Aa<aa

ex: bird clutch size(eggs/baby bird), avg infant weight, sickle cell anemia advantage

3. Disruptive: AA<Aa>aa

ex: female butterfly morphs, extreme beak sizes in seed cracker birds, adaptive radiation (finches)

Evidence for evolution

• Direct observation: Rapid evolution, short life cycles, many offspring (ex: antibiotic resistance in bacteria)

• Fossil record: simple to complex evolution, history of life using layers for timing

• Biogeography: distribution of species due to geological changes, island species, (ex: marsupials found in aussie evolved from ancestor when on mainland

• comparative morphology: vestigial structures, lost function but still found in body (wisdom teeth, femur in whales)

• comparative embryology: 

• comparative biochemistry: common genetic code, common metabolic pathways, for phylogenetic trees

comparative morphology: homologous divergence vs analogous convergence

same origin but different function vs different origin but same function (ex: wings of bugs and birds, burrowing moles, single eye lens in mollusks and humans)