Final Exam Question Themes 9-11, 19-22

Fossil Record

Provides evidence of the extinction of species, the origin and diversification of new groups, and transitional fossils, is biased and incomplete because fossilization requires burial in sediment → probability of fossilization and discovery of fossils is very low.

Likely process for the formation of simple cells

1. Abiotic synthesis of small organic molecules

2. Polymerization of small organic molecules into organic polymers

3. Formation of protocells

4. Emergence of self-replicating molecules

Fossil Record

Provides evidence of the extinction of species, the origin and diversification of new groups, and transitional fossils, is biased and incomplete because fossilization requires burial in sediment → probability of fossilization and discovery of fossils is very low.

Likely process for the formation of simple cells

1. Abiotic synthesis of small organic molecules

2. Polymerization of small organic molecules into organic polymers

3. Formation of protocells

4. Emergence of self-replicating molecules

Great Oxygenation Event

When when O2 became accumulating in the atmospheres and oceans which dramatically altered Earth’s environment. Caused the extinction of many prokaryotic groups, marking the end of the Archaean Eon.

Prokaryotic Metabolic Diversity

• Phototrophs

• Chemotrophs

• Autotrophs

• Heterotrophs

• O2 and Nitrogen Metabolism

Endosymbiotic theory

a symbiosis between two species in which one organism lives inside another organism’s cells or tissue. proteobacteria (mitochondria) and cyanobacteria (chloroplasts/plastids)

• (1°) → Prokaryotic cells are engulfed as endosymbionts by either prokaryotic or eukaryotic cells

• (2°) → Eukaryotic cells themselves become endosymbionts being taken up by other eukaryotic cells

Animal phylogeny

• All animals share a single common ancestor → an ancestral colonial flagellated protist

• Sponges are basal (primitive) animals in the phylogeny

• Eumatazoa (“true animals”) is a clade of animals with true tissues (excludes sponges)

• Most animal phyla belong to the clade Bilateria animals with bilateral symmetry (bilaterians) (mirror halves)

• Bilaterians split into 3 major clades—all are invertebrates, except Chordata, which includes vertebrates (like us with backbones)

Origin of animals

The common ancestor of animals evolved 800-650 mya and was a flagellated eukaryote.

Embrionic development sequence

• Diploid zygote undergoes a series of rapis mitotic cell divisions call cleavage, transforming the zygote into a solid ball of cells

• Cleave transforms morula into hollow blastula (hallow ball)

• Gastrulation → ‘C’ fold inwards, producing two layers of embryonic tissues (ectoderm/outer layer and endoderm/inner layer)

Hox genes

Play a fundamental role in determining the body plan and segment identity during embryonic development. Proteins coordinates the development of various structures along the anterior-posterior axis, e.g. legs, antennae.

Direct vs. Indirect development

• Direct development → animal after birth or emergence from an egg is a small version of its adult form, eg. humans

• Indirect development → has ‘larvae’ stages morphological behavioural differences from the sexually mature adult stages, eg. butterfly

Animal groupings

Invertebrates, vertebrates, body plan, diploblastic, trophoblastic, triploblastic body cavity

Coelom vs. Hemocoel

• coelom is a fluid-filled body cavity completely lined with mesoderm, found in animals like humans and worms to cushion and support organs.

• hemocoel is a blood-filled cavity found in insects and arthropods, where blood flows freely around organs in an open circulatory system.

Characteristics of eukaryotic life cycles

• Alternation between haploid and diploid stages

  • Haploid = 1 set of chromosomes (n)

  • Diploid = 2 sets (2n)

• Meiosis creates haploid cells from diploid ones

• Fertilization restores diploid state

  • Two haploid gametes fuse to form a zygote

• Mitosis helps with growth and development

• Three types of cycles:

  • Animal-like → diploid-dominant (humans)

  • Fungi-like → haploid-dominant

  • Plant-like → alternation of generations (both stages are multicellular)

Porifera characteristics

• Sessile, no tissues, motile larvae

• Water in: ostia → spongocoel → osculum

• Choanocytes trap food, amoebocytes digest/build

• Hermaphrodites, internal fertilization

• Larvae swim, development varies

Cnidaria characteristics

• Two layers, radial, one opening

• Tentacles with stingers

• Forms: polyp (still), medusa (moves)

• Clades:

  • Medusozoans: medusa

  • Hydrozoans: both

  • Scypho/Cubozoans: mostly medusa

  • Anthozoans: only polyp

Lophotrochozoa characteristics

• Includes ~17 animal phyla

• Grouped by molecular data; relationships unclear

• Body plans range from flatworms to octopuses

• No single trait shared by all

• Some have lophophore, some trochophore larvae, some neither

Lophotrochozoa phylums

• Platyhelminthes: flatworms; no body cavity or anus, e.g. planaria

• Syndermata: rotifers; tiny, pseudocoelom, ciliated crown, e.g. bdelloid rotifer

• Ectoprocta: bryozoans; sessile colonies with lophophore, e.g. Bugula

• Brachiopoda: lampshells; two shells, lophophore, e.g. Lingula

• Annelida: segmented worms with closed circulation, e.g. earthworm

• Mollusca: soft-bodied, usually shelled, e.g. octopus, snail, clam

Ecdysozoa Characteristics

• animals that molt their exoskeleton (ecdysis) e.g. arthropods, nematodes

• Defined by molecular data

• Have tough cuticles for protection of dissection (non-living, chitin)

• Nematodes = roundworms

Arthropods characteristics

• part of Ecdysozoa

• segmented body

• jointed limbs,

• exoskeleton made of chitin (e.g., insects, spiders, crustaceans), r

• reduced coelom

• open circulatory system

Deuterosomia characteristics

• group where the anus forms before the mouth in development; includes chordates and echinoderms

Chordates characteristics

• part of Deuterostomia; animals with a notochord, dorsal nerve cord, and (usually) a backbone

Echinoderms characteristics

• also Deuterostomes; marine animals with radial symmetry as adults (e.g., sea stars, sea urchins)

Parasitic rhabitophorans characteristics

• suckers/hooks for attachment to the host

• tough outer coverings

• complex life cycles involving two or more hosts: intermediate host (asexual reproduction) and definitive host (sexual reproduction)

• incl. trematodes and tapeworms

Division of Geologic Record

Hadean, Archaean, Proterozoic, and Phanerozoic