Summary
Invertebrate Diversity COMPLETE SUMMARY
- Institution
- University Of Cape Town (UCT)
Notes covering the invertebrate diversity module of the BIO1004S course.
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Chapter 33 - InvertebratesMODULE 3
• Invertebrates = animals with no spinal column (no vertebrae)
• Lack of central bony column to provide muscular attachment points
• Structure is provided by exoskeleton or hydrostatic skeleton
• Animals = heterotrophic organism that produces gametes in reproductive organs (or groups of
cells) and develops from an egg through embryo to adult, by implication, an animal is
multicellular (metazoans)
• Embryo = a newly developing individual that develops from egg to adult through one or more
stages (stage following fusion of gametes, organism then undergoes some from of
metamorphosis)
• A larva = free-living juvenile stage that is unlike the adult
• Tissue = integrated group of cells with common structure and function and in animals are
isolated from other tissues by membranous layers (eg. Nerve or muscle cells)
• An organ = a specialised centre of bodily function (may consist of several tissues): eg. Heart,
intestine, nerve cord (integration of di erent types of tissue)
• Eg. Heart = muscle, blood vessels, nerves
FUNCTIONS OF INVERTEBRATES
• Pollinators • Link between primary producers and higher
• Disease carriers consumers
• Resource acquisition • Decomposers
• Food
SPONGES/PORIFERA————————————————————————————————
CONCEPT 33.1 SPONGES ARE BASAL ANIMALS THAT LACK TRUE TISSUES
• Phylum = porifera
• Generally considered monophyletic (contested to be paraphyletic)
• Origins are near the root of the animals’ phylogenetic tree
• ∴ basal animals
• Most species = marine
• Sedentary w/ a range of sizes
• Filter feeders = lter out food particles suspended in the surrounding water as they draw it
through their bodies, often resemble a sac perforated with pores
• Water is drawn in through the pores into a central cavity (spongocoel) —> ows out of the
sponge through a larger opening (osculum)
• More complex sponges have folded body walls + branched water canals and several oscula
• Produce gametes and develop via an embryo
• Display a high degree of morphological diversity
• Upright sponges • Ball shaped
• Encrusting sponges • Bowl shaped
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, BODY STRUCTURE
• Lack true tissues (+ no organs) but have multiple cell types in their bodies
• Choanocytes = agellated cells lining the interior of the spongocoel (aka collar cells)
• Engulf bacteria and other food particles via phagocytosis
• Similarity between choanocytes and the cells of choano agellates supports the molecular
evidence suggesting that animals evolved from a choano agellate- like ancestor
• Body = two layers cells separated by a gelatinous region (mesohyl)
• Both cell layers = in contact with water
• Allows for di usion!
• Gas exchange and wast removal
• Has amoebocyte cells (use pseudopodia)
• Take up food from water and choanocytes
• Digestion
• Carrying nutrients to other cells
• Manufacture of tough skeletal bres within the mesohyl —> spicules (calcium carbonate or
silica)
• Interwoven and intricate structure
• Totipotent (capable of becoming other types of cells)
• Allows for exibility!
sponge can change shape in response to changes in environment (eg. Direction of water
currents)
• Some sponges produce exible bres (proteins called spongin)
• High complex internal structures!!
• As they get larger, complex folding of the body wall forms agellated chambers
• Increases surface area for ltering water (maximizes organic material harvesting)
• Large sponges have very little “dead space” on the inside
• Sequential hermaphrodites = function rst as one sex and then the other
• Each individual functions as both male and female in sexual reproduction by producing both
sperm and eggs
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, REPRODUCTION
• Make use of cross fertilisation
• Sperm are released into the water current by an individual functioning as a kale and drown
into a neighbouring individual that is functioning as female
• Resulting zygotes develop into agellated swimming larvae that disperse from the parent
sponge
• Then settle on a suitable substrate —> larva develops into a sessile adult
• Can be asexual (budding)
• Wall of the sponge grows and eventually breaks o to produce a replication of the parent
sponge
• Sexual (gametes) -> marine forms produce minute planktonic larvae
• zygote develops into planktonic larvae
• Has agella that become internal in a mature sponge (become choanocytes in a mature
sponge)
• Planktonic = incapable of resisting oceanic currents (drift with currents)
• Fresh water forms also produce gemmules (resting bodies) à eggs that are produced asexually
and can resist desiccation
FUNCTIONS OF SPONGES (HUMAN RELEVANCE)
• Produce a variety of antibiotics and other defensive compounds —> protection against
predators
• Eg. Cribrostatin (used to treat cancer cells and penicillin resistant strains of streptococcus)
1.Ecosystem engineers
• Engineer the environment and create habitats for other species (reefs = 3D and complex)
2. Bio-prospecting à medical
• Ability to use chemicals to protect themselves from predation
• Sponges = target organism for novel anti-viral and anti-bacterial compounds
3.Bioremediation à protection from pollution and eutrophication
• Sponges can consume the organic matter in sewage spills rendering the environment less
harmful to humans
SPONGE FEEDING
• Filter feeders —> lter out food particles suspended in the surrounding water as they draw it
through their bodies, often resemble a sac perforated with pores
CHALLENGES TO SPONGES
• FEEDING
• Choanocytes are tiny (each produce minute current)
• The same water may be sampled repeatedly
• Eggs and sperm can be cannibalized
EVOLUTIONARY RELATIONSHIPS
What evolutionary relationships do sponges have with other animal taxa
• various phylogenies based on: morphology, embryology, molecular genetics
• Choano agellates!!
• Choano agellate = main component of sponges
•Ancestor of sponges
• Colonial agellate = ancestor for metazoan lineage
• Porifera = parazoa
• Very distantly related to invertebrates
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