Animal diversity Flashcards
Diverse taxonomically
• ~3/4 of all life on earth is animal species
• ~99% of all animals species are invertebrates
• >1/2 of all living species are arthropods
• ~1/4 of all living species are beetles
Species descriptions:
- Published, peer-reviewed journal paper describing the new species.
- Type specimen of a new species deposited in a museum.
- Paratype specimens distributed among several museums.
- “Phototype” instead of actual specimen?
General characteristics of animals
Diverse in form
• From microscopic organisms to largest organism on the planet (the blue whale)
General characteristics of animals
Multicellular
• All animals are multicellular (and eukaryotic)
• Some animals have only a few cells, others millions
General characteristics of animals
- Heterotrophic
• All animals are heterotrophic
• All animals gain nutrition from external sources
• Some animals form symbiotic relationships with
photosynthetic algae
General characteristics of animals
Activity/Movement
• Most (but certainly not all) animals are active
• No rigid cell walls (as in plants)
• Flexible bodies
• Evolution of body plans that allow movement
• Muscle and nervous tissue make movement possible
General characteristics of animals
Sexual reproduction
• Most animals can reproduce sexually (although many also are capable of asexual reproduction)
• Meiosis results in (haploid) gametes
• Fertilization restores the diploid chromosome number
• No alternation of haploid/diploid generations (as in plants)
General characteristics of animals
Embryonic development and life history
• Meiosis > gametes > fertilization > zygote > embryo (morula)> blastula > gastrula)»_space;> larva or fetus»_space;> juvenile»_space;> adult
Key transition in animal evolution
Evolution of tissues
• Porifera (sponges) are loose aggregations of cells;
lack well defined tissues and organs;
• Cnidaria & Ctenophora have true tissues; but lack true organs • Platyhelminthes (flatworms) have true tissues and true organs
Key transition in animal evolution
Evolution of complex symmetry
• No symmetry (Porifera)
• Radial symmetry (Cnidaria & Ctenophora)
• Bilateral symmetry (Platyhelminthes onward)
• Bilaterial symmetry: left/right >leads to> anterior/posterior, dorsal/ventral • Leads to cephalization
Key transition in animal evolution
Evolution of segmentation
• Annelids
• Arthropods
• Chordates
Key transition in animal evolution
Evolution of body cavity (coelom)
- Parazoa:
• Porifera have internal spaces for water flow through body, but no enclosed coelomic body cavity
- Radiata:
• Cnidaria & Ctenophora have internal spaces, open to the outside, but no enclosed coelomic body cavity
- Bilateria:
• Acoelomates
• Platyhelminthes have solid body (except gut)
• Pseudocoelomates (“blastocoelomates”)
• Nematoda & Rotifera have a “simple” body cavity • Coelom partially lined with mesodermal tissue (parietal peritoneum only)
• Eucoelomates (“coelomates”) • All other Bilateria
• Coelom is a “complex” body cavity
• Coelom completely lined with mesodermal
tissue (both parietal & visceral peritoneum)
• Leads to evolution of more complex digestive tract
• Allows for gonad development and internal storage of gametes
Key transition in animal evolution
Evolution of protostome vs. deuterostome development
• Three primary developmental tissue layers
• Ectoderm (blue)
• Endoderm (yellow) • Mesoderm (red)
• Protostomes:
• Spiral cleavage
• Determinate development
• Blastopore becomes mouth (mouth first)
• In eucoelomates: Coelom derived from two clusters of
mesodermal cells that hollow out
Deuterostomes:
• Radial cleavage
• Indeterminate development
• Blastopore becomes anus (mouth second)
• In eucoelomates: Coelom derived from outpocketing of digestive tube
