Lecture 1

Porifera

Sponges.

Animals with no organs or organ systems (no brain, heart, digestive system). Sexual and asexual reproduction.

Cnidaria

Jellyfish, anemones, corals, hydra.

The common box jellyfish has gained the ability to actually move in the water, rather than drifting with the current like most jellyfish.

Ctenophora

Comb jellies.

Have cells called colloblasts that produce sticky substance to pull in prey, similar to jellyfish’s stings but not venomous.

Platyhelminthes

Flatworms, tapeworms, flukes.

Restricted to having flat shapes that allow oxygen and nutrients to pass through their bodies.

Annelida

Marine worms, earthworms, leeches.

Body segmentation increases their flexibility, some species are extremophiles, with great diversity within the phylum. Some live in really hot or cold habitats, they can also regenerate body parts.

Nematoda

Roundworms.

One species of nematode: Myrmeconema neotropicum. Targets fruit eating birds by infecting ants and turning their abdomens bright red. Birds then confuse the ants for berries and eat them, allowing the nematodes to parasitize the birds.

Mollusca

Snails, clams, octopuses, squid.

Sexual and asexual reproduction. Some have 3 hearts, snails have thousands of teeth.

Arthropoda

Lobsters, crabs, spiders, insects, centipedes, millipedes.

Have jointed exoskeletons made of chitin (skeleton on the outside). Some go through metamorphosis changing forms as they develop. Mainly sexual reproduction, asexually via parthogenesis.

Echinodermata

Sea stars, sea urchins, sea cucumbers.

Some have the ability to regenerate lost limbs.

Hemichordata

Acorn worms.

Close relative to chordates. Remarkable regenerative capabilities, can regrow bodies from fragments.

Chordata

Vertebrates, lancelets, tunicates(sea squirts).

Hollow dorsal nerve cord.

Taxonomic hierarchy

Life, domain, kingdom, phylum, class, order, family, genus, species.

Oparin-Haldane hypothesis

Primordial soup theory. Compounds of life formed over time form simple molecules present in the prebiotic environment. Simple compounds present: water Vapor, hydrogen gas, ammonia, carbin dioxide, methane, limited free oxygen. First organic molecules formed from these simple inorganic molecules and a source of energy.

Miller-Urey experiment

Stanley Miller and Harold Urey. Circulated a mixture of water, hydrogen, methane and ammonia. Energy: electrical spark. 15% of the carbon in the mixture was converted to organic compounds such as amino acids, urea and fatty acids.

Formation of polymers

Probably within semipermeable amphiphilic membranes. In aqueous solution, polymers would tend to be hydrolysed. Semipermeable membranes could provide protection.

Origin of life steps

Abiotic synthesis of small organic molecules.

Formation of macromolecules.

Packaging of macromolecules into membranes to form protocells.

Origin of self replicating molecules and true cells.

Chemical evolution

Formation of complex organic molecules from simpler ones through chemical reactions (abiotic).

Organic evolution

The process by which changes in the generic composition of population of organisms occur in response to environmental changes.

5 Darwinian evolutionary theories

Perpetual change, common descent, multiplication of species, gradualism, natural selection.

Perpetual change

Living world is always changing. Evidence: fossils. But fossils are biased cause hard structures are better preserved than soft bodied animals.

Common descent

All organisms are descended from a common ancestor (LUCA). Life’s history forms a branching tree called a phylogeny

Multiplication of species

Evolution produces new species by splitting and transforming older ones. New species form through the appearance of reproductive barriers which are biological factors that prevent interbreeding. Often arise through geographical barriers.

Patterns in macroevolution - Gradualism

Darwin. Small changes accumulate steadily over time. Sudden changes are more likely to have negative side effects. Gradualism is not alway reported by fossil records.

Patterns in macroevolution - Puntuated equilibrium

Eldridge and Gould. Long periods of stasis (equilibrium), punctuated by brief events of speciation. Speciation takes 10 000-100 000 years. Species survive 5-10 million years. Proposed in response to the lack of evidence for gradualism. Animal breeding also suggests that changes can be substantial and sudden (not gradual)

Natural selection

The process whereby organisms better adapted to their environment tend to survive and produce more offsprings. Natural selection explains adaptation.