stuff i dont know ;-;

The closest protist relatives to animals

• Both are unicellular or colonial with a collar of microvilli around a flagellum.

• Similar cell signaling and adhesion genes.

• Morphological resemblance to choanocytes (collar cells) in sponges.

choanoflagellate

Main Stages of Animal Embryonic Development

• Zygote: Fertilized egg.

• Cleavage: Rapid mitotic divisions without growth.

• Blastula: Hollow ball of cells with a fluid-filled cavity (blastocoel).

• Gastrulation: Cells migrate inward to form germ layers and the archenteron (primitive gut).

• Gastrula: Embryo with ectoderm, mesoderm (in triploblasts), and endoderm.

• Hox genes: A family of regulatory genes that control body plan development along the anterior-posterior axis.

Earliest Animal Fossils

• Ediacaran biota.

• Dated to about 558 million years ago

Radial symmetry

• Symmetry around a central axis (e.g., jellyfish)

• Suited for sessile or drifting lifestyles, can interact with environment from all sides.

Bilateral symmetry

• Left and right halves mirror each other (e.g., humans).

• Cephalization (head), directional movement, suited for active lifestyles

Asymmetry

No symmetry (sponges)

Triploblastic Body Cavity Types

• Coelomates

• Acoelomates

• Pseudocoelomate

Coelom:

Fluid-filled body cavity lined by mesoderm.

Coelomates:

Animals with a true coelom (e.g., annelids).

Acoelomates:

No body cavity (e.g., flatworms).

Pseudocoelomates:

Body cavity not fully lined by mesoderm (e.g., roundworms).

Hemocoel:

Primary body cavity in some invertebrates (e.g., arthropods), filled with hemolymph.

Hemolymph

Circulatory fluid in organisms with open circulatory systems.

Protostomes

Cells are spiral and determinate—each cell’s fate is fixed early

• blastophore becomes mouth

Deuterostomes

Cells are radial and indeterminate—each cell can develop into a complete embryo if separated

• blastophore becomes anus

Phylum Porifera

sponges

Eumetazoa

Includes all animals with true tissues, excludes sponges

How do sponges feed

filter feeding

• water enters through pores, flows into the spongocoel, and exits via the osculum. Choanocytes trap food particles with their flagella

Epithelial cells (pinacocytes)

outer covering, regulate surface area of sponge

Pores (ostia)

water enters sponge

Spongocoel

central cavity of sponge

Osculum

large opening for water exit sponge

Choanocytes

collar cells, trap food

Amoebocytes

attached to collar cells, digest food, transport nutrients, form spicules

Mesohyl

gelatinous matrix between cell layers in sponge

Spicules

structural support, deter predators of sponge

Sequential hermaphroditism

an individual functions as male and then female (or vice versa) at different times. This increases reproductive success when mates are scarce

How sponges help people

Sponges produce bioactive compounds used in cancer, HIV, and antibacterial drugs

Cnidaria

jellyfish, corals, sea anemones.

Cnidarian body forms

• Polyp: sessile, cylindrical (e.g., sea anemone).

• Medusa: free-swimming, bell-shaped (e.g., jellyfish).

• They have one opening to the gastrovascular cavity

Cnidocytes

stinging cells

nematocysts

inject toxins to capture prey or defend

Do cnidarians have a brain

No brain. They have a nerve net—a decentralized web of neurons that allows basic responses to stimuli

Bilateria

Deuterostomia, Ecdysozoa, Lophotrochozoa

Lophotrochozoa

• Lophophore: ciliated feeding structure.

• Trochophore: larval stage with cilia.

Six Lophotrochozoa

• Platyhelminthes (e.g., planaria)

• Rotifera (e.g., rotifers)

• Nemertea (e.g., ribbon worms)

• Mollusca (e.g., snails, molluscs)

• Annelida (e.g., earthworms)

• Brachiopoda (e.g., clams).

Planaria (flatworm)

• belong to Platyhelminthes. They can regenerate entire bodies from small fragments using pluripotent stem cells

• have a centralized nervous system with ganglia and nerve cords, unlike cnidarians’ nerve net

Tapeworms

in Platyhelminthes. They absorb nutrients directly through their skin from the host’s intestine

Parthenogenesis

reproduction without fertilization. In rotifers, females can reproduce asexually, allowing rapid population growth

Lophophore:

a crown of ciliated tentacles used for filter feeding in Ectoprocta and Brachiopoda

Mollusk body

1. Foot (movement)

2. Visceral mass (organs)

3. Mantle (secretes shell)

Radula

a chitinous, toothed ribbon used to scrape or cut food (not found in bivalves)

• mouth in molluscs

Mollusca

snails, clams, squids, octopuses

• Only cephalopods (e.g., octopus) have a closed circulatory system, which is more efficient for active movement

Mollusk extinction causes

habitat loss, pollution, climate change, invasive species, and overharvesting

Cnidarians vs Molluscs

Cnidarians have a gastrovascular cavity with one opening. Mollusks have a complete digestive tract with separate mouth and anus

Ecological and Economic Importance of Fungi

• Decomposers: Fungi break down dead organic matter, recycling nutrients like carbon and nitrogen.

• Pathogens: Some fungi cause diseases in plants (e.g., rusts, smuts) and humans (e.g., Candida, Aspergillus).

• Mutualists:

• Mycorrhizae: Symbiosis with plant roots enhances nutrient uptake.

• Lichens: Symbiosis with algae/cyanobacteria, colonizing harsh environments.

• Beneficial Uses: Antibiotics (penicillin), food (yeast, mushrooms), bioremediation, and industrial enzymes.

Unicellular Fungi

Yeasts

Chytridiomycota

Aquatic, flagellated spores

• Batrachochytrium

Zygomycota

Coenocytic hyphae, zygospores

• Rhizopus (bread mold)

Glomeromycota

Arbuscular mycorrhizae

• Symbionts with plants

Ascomycota

Asci with ascospores

• Saccharomyces (yeast)

Basidiomycota

Basidia with basidiospores

• Agaricus (mushroom)

Mycorrhizae

Found in soil, enhance plant nutrient uptake

Lichens

Found on rocks, trees, soil; bioindicators of air quality

Asexual Reproduction in Fungi

Budding (yeast), fragmentation, spore formation (conidia, sporangiospores).

Mating Types vs. Sexes

Fungi use mating types (e.g., +/−) instead of male/female. This reflects genetic compatibility, not gamete size or sex roles

Fungal Sexual Reproduction

Plasmogamy → Dikaryotic stage → Karyogamy → Diploid zygote → Meiosis.

Asexual spores

Mitosis, genetically identical, rapid spread

Sexual spores

Meiosis, genetically diverse, formed after plasmogamy/karyogamy

Fungal Life Cycle Stages

• Haploid (n): Most of life cycle.

• Heterokaryotic (n + n): Two nuclei coexist.

• Diploid (2n): Brief, after karyogamy.

• Heterokaryotic stage is unique to fungi

Lichen Forms

• Crustose: Flat, crusty.

• Foliose: Leaf-like.

• Fruticose: Shrubby, branched

Soredia and Lichen Reproduction

• Soredia: Asexual propagules (fungal hyphae + algal cells).

• Dispersed to form new lichens.

• Asexual reproduction