Lecture 1 The Advent of Animals

BIOL1131 Plant and Animal Biology Lecture 1 The Advent of Animals Taxonomic Classification: way of grouping biological organisms based on shared characteristics Classification of organisms is hierarchical: Kingdom, phylum, class, order, family, genus, species  kids playing catch on freeways get smashed -common names often overlap with many different species The Six Kingdoms • Monera v’s the rest? Ans= Prokaryote v Eukaryote • Plants and some protists v’s animals, fungi and some other protists? Ans=Autotrophic vs heterotrophic • Plants and animals v’s most protists and monera? Ans= Multicellular vs unicellular • Animals v’s fungi? Ans= Internal vs External digestion (absorb food from environment) • Plants and animals v’s the rest? Ans= Complex internal organs PLANTS VS ANIMALS Plants •Eukaryote • Multicellular • Autotrophic • Chloroplasts • Cells with cellulose cell walls • Mostly terrestrial • Complex organ systems Animals • Eukaryote • Multicellular • Heterotrophic • No chloroplasts • Cells without cell walls • Mostly marine • Complex organ systems Definition Animals Kingdom Animalia Multicellular – division of labour with specialised cells – in animals other than sponges, cells form tissues and organs • Embryos develop from a single celled zygote • Chemoheterotrophs - must ingest organic building blocks •Animals first evolve in sea The big breakthrough: multicellularity Three theories of animal multicellularity: 1. ciliate protist in which partitioned cytoplasm gave rise to an organism resembling a flatworm 2. flagellate protist similar to choanocytes of sponges 3. two-layered organism similar to Trichoplax 90% of animals are in these 9 phyla Phylum Example (~#species) 1. Porifera…….. sponge (8,500) 2. Cnidaria …….hydroid, jellyfish, coral (10,000) 3. Platyhelminthes……..flat worm (10,000) 4. Nematoda…….. round worm (12,000) 5. Mollusca…….. snail, mussel, octopus (100,000) 6. Annelida……. segmented worm (13,000) 7. Arthropoda……… shrimp, insect, spider (3,000,000) 8. Echinodermata…….. sea urchin, sea star (6,800) 9. Chordata……….. sea squirt, fish, frog, bird, reptile, mammal (52,000) Must know about  recall the names of these nine phyla and know: a) how to recognise animals that belong to each phyla, based on their basic characteristics b) how they are linked or differentiated by their early development and body plan Trait 1: Symmetry • Radially symmetrical animals often are (for some part of their life) non-motile (sessile), and live attached to a substrate • Bilaterally symmetrical animals have anterior and posterior ends – Promotes cephalisation, locomotion and concentration of sensory organs Cartogram of symmetry in 9 phyla = Trait 2: Germ layers and tissues • Germ layers form during embryological development – Endoderm - inner layer – Mesoderm - middle layer – Ectoderm - outer layer • Develop into tissues - aggregations of similar cells connected by an extracellular matrix – eg: muscle, blood, bone Germ layers • Animals may have – Layers of cells but no tissues OR CAN BE – DIPLOBLASTIC (two layers of cells, with tissues, but no organs) OR CAN BE – TRIPLOBLASTIC (tissues developed from three germ layers forming complex organs) Trait 3: Cleavage patterns Triploblastic animals may be Protostomes OR Deuterostomes, OR something in between, OR a mixture of the two! Protostomes and deuterostomes develop very differently There are two types of embryonic cleavage patterns, radial and spiral