animals-adaptations intro notes
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Overarching Theme – Adaptation ANIMALS – What characteristics do all animals share?What are the important trends in animal evolution?
Big Idea – Animal phylogeny (evolutionary history) is determined in part by animal body plans and adaptations.
Introduction to Animals
Characteristics Multicellular Eukaryotic Heterotrophic (ingestive) Body supported in some way – exoskeleton (invertebrates) and endoskeleton
(vertebrates)Reproduction- most animals reproduce sexually with males producing sperm and females producing eggs- some animals are hermaphrodites and can produce sperm and egg in same body- fertilization occurs when sperm penetrates the egg to produce a zygote- this can be internal – sperm and egg combine inside animal’s body – or external – egg and sperm
combine outside the body in an aquatic environment- some invertebrates show life cycles similar to plants with an alternation between sexual and
asexual phases, but not an alternation between haploid and diploid generations
i) Early Development of Embryo
-after the first cell division of the zygote, the developing animal is called an embryo- the embryo continues to undergo mitosis and forms a fluid filled ball of cells called a blastula
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- the blastula continues to undergo cell division until some cells move inward to form a gastrula= a two-cell-layer sac with an opening at one end- two branches of development have been identified in the evolution of animals
1. Protostomes – mollusks, annelids, arthropods- Mouth develops from first opening in the gastrula
2. Deuterostromes – enchinoderms, chordates- Anus develops from first opening in gastrula and mouth develops later from another
openingii) Tissue Development- the inner layer of cells in the gastrula is the endoderm, the outer layer is the ectoderm and, in some animals, cell division continues and forms a layer in between – the mesoderm
Ectoderm = Outer skin, eventually forms skin, nails, feathers and nervous system Mesoderm = Middle skin, form organs of circulatory, respiratory and urinary system, also
muscles Endoderm = Inner skin, forms gut lining, digestive organs
Body Cavities (Coeloms)-Complexity and evolutionary development can be observed by looking at the development of the body cavity-The simplest animals have a pouch–like gut with a single opening (e.g. sponge, jellyfish)-More complex animals have a gut with two distinct openings (mouth and anus) that allows for one-way flow of food through body
Coelom = fluid-filled cavity between the gut and body wall lined by mesoderm, animals possessing a coelom are called coelomates, e.g., annelids, molluscs, arthropods, key echinoderms, hemichordates and chordates, key adaptation that allows for larger and more specialized body structures
Pseudocoelom = fluid-filled body cavity lined only partially with mesoderm, instead mesoderm is present as scattered pouches in between the ectoderm and endoderm which limits tissue, organ and system development, e.g., aschelminthes
Acoelom = lack a coelom altogether, solid body without a body cavity, e.g. platyhelminthes
Symmetry (Body Plans)
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Levels of Organization-large animals need greater efficiency in body processes than small animals-cellstissuesorgansorgan systems-PoriferaCnidariaPlatyhelminthesAschelminthes, Mollusks, Annelids, Arthropods, Echinoderms, Chordates
Segmentation-In some animals, the body is externally and internally divided into segments
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Spherical Symmetry = any way you slice them, the halves will be mirror images of each
other
Radial Symmetry = from the top, if you cut them in half,
the halves will be mirror images of each other,
movement is slow, no true ‘head’ so are considered less
developed organisms, e.g. jellyfish, sea cucumber
Bilateral Symmetry = are symmetric from one side (only create mirror images if sliced in half laterally), demonstrate concentration of nerve tissue
at one end (cephalization), has ability to process
information more quickly, moves more quickly than
radially symmetric animals, in general, more complex
animals, e.g. earthwormAsymmetry = no symmetry
present: any plane that passes through the centre does not
divide them into equal halves
-an important adaptation that allows different body regions to develop for different purposes or uses Notochord- Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates and those animals which do not form this structure are called non-chordates, e.g., porifera to echinoderms.
PHYLUM PORIFERA (Sponges)General Characteristics
- no tissues or organs, but do have 4 types of specialized cells with some division of labour- limited to cell organization level, cells arranged as loose cell aggregates (cluster of cells)- sessile = do not move throughout their adult lives- look like irregularly shaped mass or branched plants (asymmetrical)- have existed for over 550 million years- their spicules are made of calcium carbonate, silica or spongin- due to lack of tissue development sponges face many limitations, have no nervous system
or brain to coordinate activities Feeding
- filter feeders, water enters body cavity through pore cells (pores=ostia)- flagellated collar cells line the inside of the body cavity- these flagella create a current that moves water containing food (plankton) and dissolved
oxygen through the sponge- water and wastes exit via osculum
- digestion occurs in collar cells that engulf food particles and store them in vacuoles- amoebocytes then distribute digested food to other cells in body, also create spicules and
produce eggs and spermReproductionSexual
- most sponges are hermaphroditic = contain both male and female gametes
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- however, only one type of gamete is produced at a time, so sponge cannot fertilize its own eggs (advantage = genetic diversity)
- sperm and eggs from sponges are released into water currents where fertilization occurs- fertilized egg --- free swimming larva (common stage in aquatic invertebrates), undergoes
metamorphosis (larval form changes shape and begins to resemble adult)--- new spongeAsexual
- budding, branching, regeneration (if sponge is pressed into sieve, cells broken up and left in sea water, cells will move around like amoebas, stick to each other and reorganize themselves back into a sponge)
- type of reproduction that occurs (sexual/asexual) depends on climatic conditions and food availability
Ecological Role- Shelter for smaller invertebrates (e.g. shrimp, fish, worms, algae)- Symbiotic relationship with photosynthetic bacteria for food and oxygen- Recycle calcium- Food source for other animals (e.g. snails and sea stars)- Indicator species for polluted oceans- Filtering action of sponges important, filters bacteria out of ocean
Confirm your learning – Sponges Vocabulary Review and Phylum Porifera Worksheet
PHYLUM CNIDARIA (hydra, jellyfish, anemones, coral…)General Characteristics
- radial symmetry- most live in saltwater, some (e.g. hydra) are freshwater- have true and distinct tissues (sign of evolutionary advancement)- only endoderm and ectoderm (no true mesoderm), instead contains mesoglea = a middle
layer of jelly-like material- gastroderm layer formed from endoderm, lines gastrovascular cavity- respond to touch, can coordinate muscle and nerve (sponges cannot)- no brain, but do have a nerve net
Feeding- basically a hollow bag with a central mouth
- (we’ll see animals with complete gut later on)- single opening, food in and waste out- fringe of tentacles surround mouth, each laced with stinging cells called cnidocytes that
shoot mini-harpoonlike devices called nematocysts
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- food target can be paralyzed if enough nematocysts are triggered- nematocysts of jellyfish cause skin irritation in humans, some have toxins that can be life-
threateningReproduction
- 2 main forms, polyp (sessile) and medusa (motile)
Sexual Reproduction (in general)o Adult male and female medusas produce gametes that are released into the watero Fertilization is external of animalo Zygote then develops into a free-swimming ciliated larva called a planulao This attaches to the sea floor and becomes a polypo Polyp buds to release young medusaso Cycle begins again
Asexual Reproductiono Some budding and regeneration, e.g. hydra and coral
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Taxonomy- unity of their body tissues is offset by the diversity of their body forms1. Class Hydrozoa (e.g. hydra and Portuguese Man-o-War), mostly polyps with a short medusa
stage, often live in colonies2. Class Scyphozoan (e.g. true jellyfish), exhibit complete alternation of generations; medusa is
dominant stage with a short polyp stage, adults move by jet propulsion
3. Class Anthozoa (e.g. sea anemones and coral), polyps only, no medusa stage, adults are sessile
Ecological Role- provide food and shelter to various marine organisms- coral reefs protect shellfish and other fish- coral reefs also protect land from erosion caused by wave action
Learning activity– Aurelia lifecycle fill in the blank sheet
Confirm your learning – work on Adopt a Spineless Wonder Group Project, due ___________
Connections to Biological Theme – Using the theme of Adaptations as a guide, explain how biologists know that animals from Phylum Porifera and Cnidaria were the first animals to evolve.
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Levels of organization give us a clue. More complex animals have specialized organs and organ systems. Sponges are in the cell level of organization; they do not have tissues or organs. Cnidaria are one level up at the tissue level of organization and therefore lack any organs or organ systems.
Another clue comes from the type of symmetry they display. Porifera are asymmetrical while Cnidarias are radially symmetric. This basically means that animals from neither of these phyla have a head and/or display cephalization seen in more complex animals._______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
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