Evo-Devo, Phylogeny, and Animal Diversity: Key Concepts and Evolutionary Processes

What are HOX genes?

Genes that encode transcription factors controlling body plan and segment identity along the anterior-posterior axis.

Why are HOX genes important?

They regulate development; small genetic changes can cause major morphological differences.

What kind of responses do HOX genes generate in organisms?

They turn other genes on/off, controlling timing, location, and identity of structures.

What are gene families?

Groups of related genes with similar DNA sequences and functions.

How do gene families come about?

Through gene duplication followed by divergence.

How does natural selection act on gene families?

Beneficial duplicates are preserved and may evolve new or specialized functions.

What role does gene duplication play in evolution?

It provides raw genetic material for new functions without losing the original gene.

What happened during the Hadean eon?

Earth formed; heavy volcanism and asteroid impacts; no life present.

What happened during the Archean eon?

First life appeared (prokaryotes); atmosphere lacked oxygen.

Why was the Cambrian Explosion important?

Rapid diversification of animals and emergence of most major animal phyla.

Why do scientists think the Cambrian Explosion happened when it did?

Rising oxygen levels, genetic innovations, and increased ecological interactions.

What are key features of prokaryotes?

No nucleus, no membrane-bound organelles, unicellular.

What are key features of eukaryotes?

Nucleus, membrane-bound organelles, often multicellular.

What did early life on Earth look like?

Simple, unicellular, prokaryotic, anaerobic organisms.

What are key characteristics of protists?

Eukaryotic, mostly unicellular, very diverse, not plants/animals/fungi.

What are the general characteristics of fungi?

Eukaryotic, heterotrophic, chitin cell walls, absorb nutrients.

How many major fungal phyla are typically covered in Bio 1114?

Five major phyla.

What is Chytridiomycota?

Mostly aquatic fungi with flagellated spores (chytrids).

What are key traits of Chytridiomycota?

Flagellated zoospores; mostly unicellular or simple multicellular forms.

Where are Chytridiomycota found?

Freshwater, moist soils; some are parasites of amphibians.

What is Zygomycota?

Mostly terrestrial molds that form resistant zygosporangia.

What are key traits of Zygomycota?

Coenocytic hyphae; sexual reproduction via zygosporangium.

Where are Zygomycota found?

Soil, decaying organic matter, food.

What is Glomeromycota?

Fungi that form arbuscular mycorrhizal associations with plants.

What are key traits of Glomeromycota?

Obligate mutualists; form arbuscules inside plant roots.

Where are Glomeromycota found?

In plant roots in most terrestrial ecosystems.

What is Ascomycota?

Sac fungi that produce spores in asci.

What are key traits of Ascomycota?

Asci; often reproduce asexually; includes yeasts and molds.

Where are Ascomycota found?

Soil, plants, aquatic habitats, as symbionts or pathogens.

What is Basidiomycota?

Club fungi that produce spores on basidia.

What are key traits of Basidiomycota?

Basidia; complex fruiting bodies such as mushrooms.

Where are Basidiomycota found?

Soil, wood, forests, and many terrestrial habitats.

What are key characteristics of land plants?

Cuticle, stomata, protected embryos, alternation of generations.

What is alternation of generations?

A life cycle alternating between haploid gametophyte and diploid sporophyte.

What is the ploidy of the gametophyte?

Haploid.

What is the ploidy of the sporophyte?

Diploid.

What are the main characteristics used to define animal phyla?

Body symmetry, tissues, body cavity, segmentation, and development.

What are the four chordate synapomorphies?

Notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail.

What distinguishes jawless fishes (Agnatha)?

Lack jaws; eel-like bodies (lampreys, hagfish).

What innovation defines jawed vertebrates (Gnathostomes)?

The evolution of jaws.

What is ecology?

The study of interactions between organisms and their environment.

What is symbiosis?

A close, long-term interaction between species.

What is parasitism?

One species benefits, the other is harmed.

What is mutualism?

Both species benefit.

What is commensalism?

One species benefits, the other is unaffected.

What is mimicry?

One species evolves to resemble another.

What is coevolution?

Reciprocal evolutionary change between interacting species.

Chytridiomycota

Flagellated zoospores; mostly unicellular or simple multicellular forms.

Chytridiomycota Habitat

Freshwater, moist soils; some are parasites of amphibians.

Chytridiomycota Life History

Decomposers or parasites.

Zygomycota

Mostly terrestrial molds that form resistant zygosporangia.

Zygomycota Key Traits

Coenocytic hyphae; sexual reproduction via zygosporangium.

Zygomycota Habitat

Soil, decaying organic matter, food.

Zygomycota Life History

Mostly decomposers; some parasites.

Glomeromycota

Fungi that form arbuscular mycorrhizal associations with plants.

Glomeromycota Key Traits

Obligate mutualists; form arbuscules inside plant roots.

Glomeromycota Habitat

In plant roots in most terrestrial ecosystems.

Glomeromycota Life History

Mutualistic symbionts with plants.

Ascomycota

Sac fungi that produce spores in asci.

Ascomycota Key Traits

Asci; often reproduce asexually; includes yeasts and molds.

Ascomycota Habitat

Soil, plants, aquatic habitats, as symbionts or pathogens.

Ascomycota Life History

Decomposers, parasites, and mutualists (lichens).

Basidiomycota

Club fungi that produce spores on basidia.

Basidiomycota Key Traits

Basidia; complex fruiting bodies such as mushrooms.

Basidiomycota Habitat

Soil, wood, forests, and many terrestrial habitats.

Basidiomycota Life History

Decomposers, parasites (rusts and smuts), and mutualists.

Porifera

Asymmetrical; no true tissues; porous body; filter feeders.

Porifera Example Species

Sponges (e.g., bath sponge).

Cnidaria

Radial symmetry; true tissues; diploblastic; cnidocytes with stinging nematocysts.

Cnidaria Example Species

Jellyfish, sea anemones, corals.

Platyhelminthes

Bilateral symmetry; triploblastic; acoelomate; flattened body.

Platyhelminthes Example Species

Planarians, tapeworms, flukes.

Nematoda

Bilateral symmetry; pseudocoelom; unsegmented round body; complete digestive tract.

Nematoda Example Species

Roundworms, hookworms, C. elegans.

Annelida

Bilateral symmetry; true coelom; segmented body; complete digestive tract.

Annelida Example Species

Earthworms, leeches, polychaete worms.

Mollusca

Bilateral symmetry; true coelom; mantle, muscular foot, visceral mass; many with shells.

Mollusca Example Species

Snails, clams, octopus, squid.

Arthropoda

Bilateral symmetry; segmented body; jointed appendages; chitinous exoskeleton.

Arthropoda Example Species

Insects, spiders, crabs, centipedes.

Echinodermata

Radial symmetry (adults); water vascular system; endoskeleton; marine only.

Echinodermata Example Species

Sea stars, sea urchins, sand dollars.

Chordata

Notochord; dorsal hollow nerve cord; pharyngeal slits; post-anal tail.

Chordata Example Species

Fish, amphibians, reptiles, birds, mammals.