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Symmetry
arrangement of body parts in relation to the central axis
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Radial
- animal may be divided into any number of equal halves only along the central longitudinal axis
- -like cylinder with different top and bottom
- -ex., jelly fish
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Bilateral
- body parts usually in pairs on either side of the sagital axis
- (1) can be divided into two parts only along that axis
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Terms for bilateral animals
- anterior – head end
- (i) Contains brain and concentration of sensory structures
- posterior – tail end
- dorsal – back side – faces up
- ventral – belly side – faces down
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Body Cavities
- Acoelomate
- pseudocoelomate
- eucoelomate
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Acoelomate
- no body cavity
- body filled with jelly-like substance
- ex. flat worms
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pseudocoelomate
- false” body cavity
- have a body cavity but not lined with membrane
- pseudocoelom is filled with fluid
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eucoelomate
- “true coelom”
- have a body cavity lined with membrane
- ex. everything after roundworms
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Segmentation
- bodies divided into segments
- may all be very similar to each other
- (ex. earthworm
- (may be specialized groups
- ex. crayfish
- not obvious in chordata (ex. humans)
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Introduction to Animal Diversity
- Over 1.5 million species named
- b) Less than 20% of species that exist
- c) Over 99% are invertebrates
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Phylum Porifera – Sponges
- Simplest Animals in terms of anatomy
- multicellular but lack true tissues or organs
- all processes occur at the cellular level
- all aquatic - mostly marine - a few fresh water
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Cindaria - Jellyfish, coral and their relatives
- name means stinging cells – all have them
- ii) hollow sac-like body
- iii) radial symmetry
- iv) All aquatic - most marine
- v) have tissues and primitive nervous and muscle systems (unlike sponges )
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2 main body types of cindaria
- polyp
- ex sea anemone
- Medusa - umbrella shaped
- ex jelly fish
- iii) some cnidarians are always one body type, others alternate in life-cycle
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Platyhelminthes - flat worms
- Characteristics
- Bilateral symmetry
- three tissue layers
- simplest animals with organ system level of complexity
- Acoelomate
- incomplete digest. syst. (if present)
- no resp. or circ. syst. - gasses diffuse across tegument
- simple – ladder-like nervous system
- flame cells for excretion
- osmoregulation in aquatic spp.
- nearly all are monoecious (both sexes in one individual)
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types of flat worms
- free - living
- (1) ex. Planaria sp. (fresh water)
- flukes - trematodes
- tapeworms
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flukes - trematodes
- parasitic - complex life cycles
- (adults reproduce sexually in vertebrate host
- asexual reproduction in snail host
- ex. Schistosoma sp.
- (a)Causes human disease schistosomiasis
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tapeworms
- adults - parasites in intestine of vert.
- lack digestive system
- absorb nutrients through body wall – like inside out intestine
- complex life-cycles
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Phylum Nematoda - round worms
- Huge phylum
- all habitats - fresh, marine, terrestrial (soil), many parasitic
- nearly all animals have a nematode parasite
- Characteristics
- Pseudocoelomate
- cavity has several functions
- Hydrostatic skeleton - liquid pressure gives support, protects organs, movement, circulation of nutrients, gasses
- lack circulatory and respiratory systems
- complete digest. syst.
- reproduce sexually
- sexes usually separate (dioecious)
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some parasitic nematodes of medical importance
- Ascaris lumbricoides – large roundworm of humans
- Pinworm - ubiquitous
- Filarial worms - not a direct life cycle - insect host
- ex - dog heart worm
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Phylum Mollusca
- a)eucoelomate
- b)mostly marine - many fresh water and some terrestrial
- c)most have shell of CaCO3
- i)secreted by mantle
- d)soft body with muscular foot and visceral mass
- e open circ. syst. –
- i)exception: squid and octopus
- f)Reproduce sexually - most dioecious
- g)respiration – gills in most,
- h)examples
- i)clams and relatives - shell of two valves - bivalves (class)
- ii)snails and their relatives - one shell foot
- iii) Squid and octopus
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Phylum Annelida - segmented worms
- eucoelomate
- b) true segmentation
- c) closed circ. syst.
- d) excretion by nephridia
- e) nerv. syst. with . ventral nerve cord and cerebral ganglia
- f) sexual repro.
- g) groups
- i)earthworms - terrestrial and aquatic
- ii)polychaeta - almost all marine
- iii) leaches
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Phylum Arthropoda
- a) most successful group of animals
- i) mostly due to the insects
- b) name means jointed appendage
- c) segmented –
- i) seg. specialized
- d) exoskeleton of chitin
- e) most repro. sex. - most dioecious
- f) open circ. syst.
- g) groups
- i) trilobites
- (1)extinct
- (2)in fossil record
- ii)spiders and relatives (scorpions, mites, ticks)
- (1)4 pairs of walking legs (eight total)
- iii) insects
- (1)usually 3 pairs of walking legs and 1 or 2 pairs of wings
- (2)extremely diverse
- (3)most undergo some metamorphosis
- (a) complete - egg, larva, pupa, adult
- (i) ex. flies, butterflies
- (bincomplete - egg - larval stages - adult
- (i) ex. grasshoppers
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crustaceans - shrimp, lobster, crayfish, crabs
- mostly aquatic -
- most resp. by gills
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Phylum Echinodermata - Name means spiny skin
- Characteristics
- i)Have pentaradial symmetry (parts arranged in fives around central axis) as adults
- ii)Bilateral symmetry as larvae
- iii) Early devel. sim. to chordates
- iv) Have water vascular system - unique to phylum –
- b) Examples
- i) Starfish
- ii) sea urchins
- iii) brittle stars
- iv) sea lilies (crinoids)
- v) sea cucumbers
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Phylum Chordata
- mostly vertebrates – animals with backbones
- b) Characteristics– all have during some part of their development
- i) Notochord – dorsal rod that supports the body – only in embryonic vert.
- ii) Dorsal, hollow nerve cord – becomes brain and spinal cord in most
- iii) Pharyngeal gill slits
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Invertebrate chordates – have above char.
- Tunicates (sea squirts) – mostly marine, mostly sessile as adults, filter feeers, many are colonial
- ii) Lancelets – fish-shaped invertebrates, marine, filter-feeders
- iii) Probably closest relatives of the vertebrates
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Vertebrate chordates Groups
- 3 classes of fish – all aquatic, no legs
- Other groups are all tetrapods (4-legged) - most terrestrial
- Amphibians– frogs, salamanders etc
- Reptiles – snakes, lizards, turtles, etc
- Birds – evolved from reptiles
- Mammals
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Amphibians– frogs, salamanders etc.
- breed and lay eggs in water where larval development occurs (ex tadpole)– become adults and move onto land
- ectothermic= cold blooded
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Reptiles – snakes, lizards, turtles, etc
- Have totally terrestrial life history
- (b)Adaptations
- (i) scales of keratin to prevent desiccation,
- (ii)amniote egg
- 1. shell to prevent des.
- 2. stores wastes in a non-toxic way
- 3. stores nut. for dev. of embryo
- ectothermic= cold blooded
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Birds – evolved from reptiles
- (a Have amniote egg
- (bscales on legs
- (c)and beaks of keratin
- adapted for flight
- (i) feathers
- (ii)hollow bones
- (iii) requires a lot of energyendothermic = warm blooded
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(aEmbryonic development is internal – in females
- (b)Mammary glands on female for care of new-born
- (c)Body with hair
- (d)endothermic
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