History of life on earth

What is the Phanerozoic?

The paleozoic, mesozoic, and cenozoic.

What is archaean earth and what occured during it?

A period 4.5-2 billion years ago. Cyanobacteria formed stromatolites and caused the great oxidation event.

What is snowball earth and what occured during it?

An ice age 717 million years ago, entire planet covered in glaciers which ground mountains and released minerals into the water.

What is the ediacaran and what occured during it?

A period from 635-540 million years ago, saw the development of the first complex multicellular life.

What is the cambrian and what occured during it?

A period from 539-495 million years ago, saw the rise of most of the Big Nine during the cambrian explosion.

What is the ordovician and what occured during it?

A period from 495-444 million years ago, the first plants reached land and the Great Ordovician Biodiversification Event occured. A mass extinction caused 85% of all life to die.

What is the silurian and what occured during it?

A period from 444-419 million years ago, the first jawed fish arose and invertebrates arrived on land.

What is the devonian and what occured during it?

A period from 419-359 million years ago, amphibians arrived on land and so did the first trees. A possible asteroid impact caused an extinction.

What is the carboniferous and what occured during it?

A period from 359-299 million years ago, coal deposits formed and the first synapsids evolved.

What is the permian and what occured during it?

A period from 299-250 million years ago, the worst mass extinction in earths history.

What is the triassic and what occured during it?

A period from 249-201 million years ago, the first dinosaurs evolved.

What is the jurassic and what occured during it?

A period from 201-145 million years ago, diversification of dinosaurs and the rise of birds.

What is the cretaceous and what occured during it?

A period from 145-65 million years ago, first flowering plants and grasses evolved, K-T extinction.

What are synapomorphies?

Shared, derived traits.

What is the theory of panspermia?

The idea life came from another planet.

What are 2 ideas for how life arose?

Primordial soup, hydrothermal vents.

What is the RNA-world hypothesis?

Early organisms would have relied solely on RNA both for genetic information and catalysing reactions.

What is a microbiome?

The community of microbes that live in/on another organism.

What is a metagenome?

The collective set of all genomes in a microbiome.

How do prokaryotes reproduce?

Binary fission (splitting in half).

How can prokaryotes create biofilms?

Attaching to one another using appendages called fimbrae, S-layers, or producing capsules.

What is a phototroph?

Gains energy from sunlight.

What is a chemotroph?

Gains energy from chemicals.

What is a organotroph?

Gain electrons from organic sources.

What is a lithotroph?

Gain electrons from inorganic sources.

What is a autotroph?

Uses CO2 to create organic compounds.

What is a heterotroph?

Use organic compounds from the environment.

What enzyme fixes nitrogen in prokaryotes?

Nitrogenase.

What shapes can prokaryotes be?

Rods (bacilli), spheres (cocci), corkscrew (spirochaetes), spiral (spirilla), comma (vibrios).

How can the shapes of prokaryotes be arranged?

Chains, clusters, pairs.

How much methane do archaea produce every year?

1 billion tonnes.

What is the endosymbiotic theory?

An aerobic prokaryotic microbe was ingested into a heterotrophic anaerobe (likely asgard archaea), producing eukaryotes.

What are protists?

A polyphyletic group of all eukaryotes which are not plants, fungi or animals.

What is algae?

Photosynthetic organisms which are not plants.

How did algae evolve?

A eukaryote engulfed a cynaobacterium (primary endosymbiosis), and was then engulfed by a second eukaryote (secondary endosymbiosis).

What defines supergroup Excavata, and what groups is it split into?

Some members have an excavated feeding groove on their side. Split into metamonada, discobids (identified by a rod with a spiral structure in their flagellum) and malawinomadida.

What defines supergroup hapista and what groups is it split into?

Defined by having two slightly uneven flagella, and a calcium carbonate coccolith shell. Split into stramenopiles, alveolata, and rhizaria, together making up half of eukaryote diversity.

What defines the supergroup stramenopiles, and what does the group include?

Have a hairy flagellum and a smooth flagellum. Include diatoms, algae with a glass-like silica wall. Includes brown algae, called seaweed. Includes oomycetes.

What is the structure of brown algae?

Body (Thallus), Roots (Holdfast), Stem (Stipe), and Leaves (Blades).

What defines the supergroup alveolata and what does it contain?

Defined by presence of alveoli under plasma membrane. Include dinoflagellates (responsible for bioluminescence, have cellulose plate armour), Include apicomplexa (largely parasites), Include ciliophora (use cilia to move and feed).

What defines the supergroup Rhizaria, and what does it contain?

Some posses a mineral exoskeleton. Includes foraminifera (characterised by external shell ‘test’).

What defines supergroup archaeoplastida and what does it include?

Includes red algae (rhodophyta), green algae (chlorophyta) and plants.

What defines supergroup amorphea and what does it include?

Defined by having a single emergent flagella. Includes amoebae (slime moulds). Includes opisthokonts (animals and fungi).

What defines metazoa?

Having eukaryotic cells, being multicellular, different cells having different functions, cells organised into tissues and organs, early embryos form tissue layers, heterotrophic.

What was the growth of life in the Ediacaran called?

The avalon explosion.

When did biomineralization evolve, and how do we know?

The ediacaran, due to the presence of cloudina.

What are 4 ediacaran species and their presumed phylogenies?

Dickinsonia and Sprigginia (bilateral but unknown phylogeny), Tribrachidium (no descendants), Kimbrella (early mollusc).

What are the parazoa?

Primitive animals at the base of the tree of life, includes porifera.

What is phylum ctenophora?

Comb jellies, related to cnidaria due to radial symmetry and diploblastic nature.

What is phylum placozoa?

Flat animals with only 4 cell types, eat by exuding digestive enzymes.

What two sites are key for cambrian fossils?

Burgess shale (canada), chengjiang (china).

What are possible biotic causes for the cambrian explosion?

Predation and food webs, evolution of swimming, evolution of burrowing, evolution of segmentation, evolution of eyes.

What are possible abiotic causes for the cambrian explosion?

Biomineralization, Sea level rise, Substrate oxidation, Increase in marine environments.

What did early exoskeletons use?

Aragonite, an alternate form of calcium carbonate.

What caused the cambrian extinctions and what evidence fuels this?

Volcanic activity. Rocks show high levels of sulphur, and a band of iridium.

When did coral reefs arise?

The ordovician.

What subphylum do corals belong to?

Anthozoa.

What groups is anthozoa split into?

Hexacorallia (stony corals, use aragonite), Rugosa (largely solitary, extinct), and Tabulata (colonial, extinct).

What are graptolites?

Members of phylum hemichordata, became ocean sailors eating plankton.

What is phlum brachiopoda?

Brachiopods, evolved in cambrian and diversified in ordovician. Been in decline since the permian. Attach to sea floor through a pedicle.

When did cephalopods undergo diversification?

The orodovician, with the rise of nautiloids and orthocones.

When did echinoderms arise?

The ordovician.

When did agnatha (jawless fish) diversify?

The silurian.

What were eurypterids?

The earliest chelicerates, which ventured onto land in the silurian.

What are fungi?

Eukaryotic Heterotrophs.

What are yeasts and how many species are there?

Single celled fungi. 1500-2000 species.

What are molds and mildews and how many species are there?

Single celled fungi. 100,000 species.

What are macrofungi?

Fungi species which produce large fruiting bodies (e.g. mushrooms).

What are mycorrhizal fungi?

Fungi which perform a symbiotic relationship with plant roots.

When did fungi evolve and when did they arrive on land?

Evolved 1.2-1.5billion years ago, arrived on land 635 million years ago.

What are ectomycorrhizas?

Mycorrhizal fungi whos hyphae move around root cells.

What are endomycorrhizas?

Mycorrhizal fungi whos hyphae move into root cells.

What did saprotrophic fungi do?

Evolved lignin-degrading enzymes, allowing breakdown of wood and causing the end of the carboniferous.

Why is the fungi fossil record so patchy?

Mycelium decays very quickly.

What are prototaxites?

Possibly 8m tall fungi.

What is the rhynie chert formation?

A devonian (410mya) fossil site in aberdeenshire.

How many fungi are known and how many are estimated to exist?

150-200,000 known, 2.2-3.8million expected.

What are chytridiomycota?

A lineage known for disease of amphibians, possess zoospores which can swim through water.

What are zoopagomycota?

A lineage known to act as parasites of other fungi, arthropods, etc.

What are mucoromycota?

A lineage known for molds and mycorrhizas. Helped plants to arrive on land.

What are ascomycota?

A lineage which forms a sac-like ascus, containing ascopores.

What are basidiomycota?

A lineage of filamentous fungi which produce a sporocarp (or mushroom) containing basidiopores.

What are saprotrophic fungi?

Fungi which break down biomass using a range of molecules.

What are entomopathogenic fungi?

Fungi which specialise in infecting arthropods.

What are mycophagists?

Animals which eat fungi.

What are lichens?

Symbiosis between a fungus and an algae/cyanobacterium. Can be crustose, fruiticose or foliose.

What are conodonts?

Jawless fish discovered from ‘conodont elements’. Long, eel-like bodies with a notochord, paired sensory organs, fins with fin rays, and v-shaped muscle blocks.

What is special about conodont elements?

Have both dentine and enamel structures, features seen in jawed vertebrates. Believed to have evolved crown mineralization independantly of other vertebrates.

What are hagfish?

Jawless cyclostomes with a cartilagenous skull and arcualia (precursors to vertebrae).

What are lampreys?

Jawless cyclostomes with vertebra-like structures and fin rays.

What is the relationship between conodonts and cyclostomes?

Recent phylogenies place conodonts as basal cyclostomes.

What are ostracoderms?

A paraphyletic group of jawless armoured fish.

What are heterostracanas?

Ostracoderms with head shields and a mineralized dermal skeleton.

What are anaspids?

Ostracoderms with limited armor but long, regularly arranged scales.

What are thelodonts?

Ostracoderms with scales and no armor.

What are galeaspids?

Ostracoderms with mineralized neurocraniums, allowing brain anatomy to be preserved.

What are osteostracans?

Ostracoderms with paired pectoral fins, perichondral ossification and heterocercal tail.

What is the differenc between a heteroceral tail and homocercal tail?

Heterocercal tails have a longer top half.

What are Placoderms?

Jawed fish. Split into arthrodires (included dunkleosteus) and antiarchs (which has arthropod-like arms for digging/walking).

What are acanthodians?

Spiny sharks with heterocercal tails.