Overarching Theme – Adaptation ANIMALS – What characteristics do all animals share?What are the important trends in animal evolution?

Big Idea – As Flatworms, Roundworms and Mollusks have evolved, adaptations such as three germ layers, coeloms, cephalization and complete digestive tracts

show an increase in the complexity of animals.

PHYLUM PLATYHELMINTHES (FLATWORMS) – Unsegmented WormsGeneral Characteristics- bilateral symmetry- acoelomates- dorso-ventrally flattened- three tissue layers including mesoderm and true organs- no respiratory or circulatory system, gases exchanged through diffusion- cephalization- free-living and parasitic forms (2/3 of all species!)TaxonomyA) Free-Living Forms: Class Turbellaria (Planaria) - freshwater, mud or damp soil habitats- free-living- vary in colour, size and form, can be 1-60 cm in length - covered with cilia

i) Feeding- only a mouth, no anus - small food swallowed whole through the pharynx, an extendible tube ending in the mouth, pharynx is

located ½ way down body on stomach- excretion through fine tubules called flame cells that open to outside via small pores, evolutionary

significant as it shows increased specialization in body structuresii) Nervous System- primitive brain (essentially, nerve tissue concentrated at head) and two nerve cords coordinate body movements- eyespots on anterior end, light detection only, not image forming- demonstrates negative phototaxis (=avoids light), response to chemicals and the ability to ‘learn’iii) Reproduction- Sexual, are hermaphroditic, but two animals have to fertilize each other (can’t self-fertilize)- two worms join together and pass sperm to each other, eggs fertilized internally and released as cocoons

into water where they hatch within a few weeks -Asexual, can regenerate complete worms from fragments, if flatworm is split in two, front and back halves

will form into new worms

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B) Parasitic Forms (Tapeworms and Flukes) - long and ribbon-like- live inside (organs) or outside (skin, mouth, gills) body of a host- sensory receptors are absent or reduced- have a tegument or cuticle for protection against enzymes in the intestine- most are hermaphrodites - go through at least two stages in their life cycle- have a primary host that contains the adult, sexually reproducing worms- also have an intermediate host, that contains immature forms of worm

i) Feeding- parasitic life style diminishes need for specialized digestive structures so little or no digestive tract is present since it eats predigested food from host, food absorbed through skinii) Reproduction- most complex system in their body- absence of digestive tract makes room for hundreds of thousands of eggs- ripe section of worm (one full of eggs) detaches itself and passes out of host in feces

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iii) Taxonomy Flukes (Class Tremadoda)

- life cycle involves two or more different hosts- Blood Flukes affect humans, intermediate host is a snail- victims may become weak and may die

Learning Activity – Investigation Bilharzia Sheet and Cnidaria, Playhelminthes, Nematoda Stations Lab

Tapeworms (Class Cestoda) - can be up to 18 m long!- weakens, but doesn’t kill host- live in intestine of vertebrate animals- has a scolex = at the head, suckers and a ring of hooks to attach to intestinal wall- body composed of proglottids = body sections containing a full set of male and female sex organs

- young sections near scolex; older, more mature ones at posterior- each section contains 100,000 eggs!- each section can break free from rest of worm, therefore different from segmentation seen

in more complex worms- can self-fertilize (adaptation accommodating their solitary lifestyle) or fertilize other

tapeworms

- Life Cycle of Beef/Pork Tapeworm (see diagram)1. eggs of tapeworm released in animal (human) feces2. animal drinks water polluted by sewage3. eggs mature inside cow (intermediate host), 4. embryos bore into muscle tissue and form a cyst

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5. undercooked, rare meat consumed by human6. worm emerges from cyst in human’s intestine, attaches to intestinal wall,7. grows and produces eggs in proglottids

PHYLUM ASCHELMINTHES/NEMATODA (ROUNDWORMS) – Unsegmented WormsGeneral Characteristics- pseudocoelomate- three tissue layers and true organs- bilateral symmetry- complete digestive system (mouth and anus), important step in evolution- anterior ganglion (= collection of nerve cells) and lateral or ventral nerve cords- no respiratory or circulatory system, gases exchanged through diffusion- free-living and parasitic forms- long cylindrical body with pointed ends, featureless body with tough skin- sexes are separate (dioecious), i.e., males and females are distinct- sexual reproduction most common, with internal fertilization

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i) Parasitic Forms - Example Ascaris lumbricoides (see diagram)- internal parasite of pigs and humans- lives in stomach, feed on partially digested food

1. human consumes water/unwashed vegetables contaminated with human waste and swallows eggs

2. eggs hatch in intestine 3. new larvae penetrate gut wall -> enter circulatory system 4. migrate to liver (hepatic portal), heart and lungs of host -> grow in lungs5. travel up windpipe 6. swallowed and down back down into intestine 7. worms mate and fertilized eggs come out with feces

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Learning Activity – Ascaris Dissection

Ecological Role- one spadeful of soil may contain one million roundworms!- many adaptations to live in variety of habitats- some species cause diseases in animals (Ascaris spp., pinworms, heartworms) and plants (nematodes)- important role in food chains; some consume organic matter, some are a food source, parasitic worms weaken hosts and cause them to be more easily caught by predators – an adaptation that may help in the distribution of the parasite

PHYLUM MOLLUSCA – MollusksMollus = Latin for softExamples = clam, squid, slug, nudibranch, chitons, garden slugs, octupus…General Characteristics- bilateral symmetry- coelomates- complete digestive tract

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- reproduce sexually- development of an endochrine system - rely on blood to deliver hormones (chemical signals) to necessary organs- all seven classes have common body plan that separates them from other invertebrates

o foot – for locomotion (some divided into tentacles)o shell – CaCO3 for protection (internal or external)o mantle – tissue fold covering body, outer layer of body wall that secretes shello gills – respiratory structures, lie between body and mantleo visceral mass – contains internal organs and organ systems

Taxonomy Classes

A) Gastropods, include slugs, snails, abalone and nudibranches - Most have protective, one piece shell- if no shell, secrete toxins or hide in dark places to protect themselves- nudibranches are brightly coloured and have nematocysts to ward off predatorsi) Feeding and Digestion- herbivores- use radula (tongue-like organ) to scrape bits of vegetation into mouthii) Circulation- open circulatory system (blood not confined in vessels)- blood pumped out of vessels into open spaces surrounding organs- two-chambered heart- efficient gas/nutrient/waste exchange for slow moving animalsiii) Respiration - terrestrial species, exchange gases through diffusion in mantle cavity- aquatic species, use gillsiv) Excretion- nephridia localized in one region (as opposed to segments throughout body as with annelids)- after they filter blood, waste is passed out through mantle cavityv) Nervous System- since are motile, do have some response to stimuli- light sensitive “eyes” mounted on retractable antennae- cephalizationvi) Movement- very slow moving- use muscular foot on ventral side that contracts in rippling motion- secrete mucus to slide over surfacesvii) Reproduction- hermaphrodites but must cross fertilize- similar mating behaviour to annelids, shows evolutionary link- babies hatch directly from fertilized egg, no larval stage (as in annelids)- two worms crawl into mating position and transfer sperm to sperm receptacle of each other- worms separate- mature ova and sperm shed in cocoon, fertilization external

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viii) Ecological Role- biological research is investigating why snails never develop cancer, may gain insights in how to fight cancer in other animals- intermediate hosts for parasitic worms, e.g. snails and slugs are intermediate hosts for flukes- important food sources in food chains

A) Bivalves , include clams, oysters and scallops i) Feeding and Digestion- have adapted to life as filter feeders- food particles become attached to mucus on gill membrane- cilia move food to mouth - food then moves through esophagus to the stomach- protein and fat digestion is within a digestive gland- carbohydrate digestion in stomach- carnivorous mollusks use radula to drill through shells of their preyii) Circulation- open circulatory system, same as gastropodsiii) Respiration and Excretion (pretty much intercombined)- siphon (double tube) extends from body into water- one tube takes in water with O2 and nutrients, washes over gills and body tissues- other tube takes CO2 and wastes (from anus) and flushes out of body- siphon can retreat into body and retain water for survival when tide is out - nephridia, as with gastropodsiv) Nervous System- since are mostly sessile, fairly simple for bivalves - most have eyespots along edges of shell- mouth, foot and viscera each have a pair of ganglia, each is thought to be sensitive to different stimuli

o foot, balancing gangliao viscera, ganglia sensitive to chemicals

v) Movement- have two shells hinged together by muscles - mostly sessile but if under threat can swim by rapidly opening and closing their shells or by using muscular foot to burrow into sedimentvi) Reproduction- have separate sexes- as with most sessile aquatic organisms, fertilization is external- fertilized egg develops into ciliated larva stage called a trocophore- swims around until it finds suitable location to grow into adult form- similarity of larval stages in bivalves and annelids show evolutionary linkvii) Ecological Role- form critical links in the food web/chain since are source of food for fish, seastars, birds, humans and other mammals

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- recycle nutrients, e.g. mussel recycles sediment back into the environment- some are keystone species, required to maintain healthy ecosystems- nacre (=smooth inner surface of shells) builds up in many layers to produce pearls in oysters

C) Cephalopods, include octopi, squid, nautiluses and cuttlefish - most lack a protective shell, but move very rapidly- mantle is internal and produces a bony plate that protects the brain- squid squirt ink to confuse predators and octopi can change their body colour/texture/pattern to blend in with environmenti) Feeding and Digestion- predators- have eight or more tentacles (some nautiluses have 90+!) equipped with suction cups or sticky mucus to grab and hold prey- use radula to tear up prey and ingest or beaks to stab and immobilize preyii) Circulation- fast moving animals so require a more efficient circulatory system - have a closed circulatory system with blood contained in vessels as it moves throughout the body- three-chambered heartiii) Respiration- use gills to exchange gasesiv) Excretion- use nephridia for metabolic waste removal- complete digestive system, so solid wastes out anusv) Nervous System- since they move more quickly they require a more highly developed brain, they even have a memory and can learn- well developed eyes, especially the squid which rivals mammals in its visual abilityvi) Movement- use jet propulsion- change direction quickly when swimming by alternating direction of its siphon- can move by crawling along the ocean floor or sea bed with their armsvii) Reproduction- separate sexes with internal fertilization- fertilized eggs released by female into open waterviii) Ecological Role- top predators in some ecosystems so play role in limiting population growth of prey species

Connections to Biological Theme – Describe the evolutionary advantage of the complete digestive tract, first seen in roundworms.It permits food being taken in mouth at same time as food leaves body through anus – animals can eat more, get more nutrients and energy to get bigger and move more quickly.Also allows for areas of specialized function in the digestive tract. Different parts of the system are adapted for different function such as nutrient absorption, enzyme breakdown of food, waste excretion and water retention.

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How did the development of the coelom allow for adaptations in mollusks that were not possible in earlier animals?Coelom provides a chamber for the blood vessels and a heart, excretory organs and (in some) respiratory organs.__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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