Worms Chapter 1 Section 4. What Worms have in Common What are the 3 major phyla of worms we are...

Worms

Chapter 1 Section 4

What Worms have in Common

• What are the 3 major phyla of worms we are discussing?– Flatworms– Roundworms– Segmented worms

Flatworm

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Flatworms

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Flatworm

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Roundworm

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Segmented Worms

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Segmented Worms

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Segmented Worms

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What Worms have in Common

• Which phylum do flatworms belong to?– Platyhelminthes

• Which phylum do roundworms belong to?– Nematoda

• Which phylum do segmented worms belong to?– Annelida

What Worms have in Common

1. Invertebrates

2. Long, narrow bodies without legs

3. Have tissues, organs, and organ systems

4. Bilateral symmetry

5. Head and tail end

Worms

• Do worms have a brain?– Yes– Simplest organism with a brain– Knot of nerve tissue located in the head end– Detect food, mates, and predators quickly– Responds to the information from the brain

Reproduction

• How do worms reproduce?– Sexually

• Male and female worms = sexually• Have both sex organs – 2 worms mate and

exchange sperm• Break into pieces – asexually

– Earthworms can’t do this

• Regeneration : – Ability to regrow body parts

Flatworms

• Flat bodies

• Examples:– Planarians– Flukes– Tapeworms

• Bodies soft like jelly

• Almost too small to be seen except tapeworms can grow to 12 meters

Flatworms

• Most are parasites that obtain food from their hosts

• Parasite:– Organism that lives inside or on another

organism

• Host:– The organism that a parasite lives on or in – The parasite takes nutrients from the host

Tapeworms

• 1 kind of parasitic flatworm

• Absorbs food from the host’s digestive system

• Most live in more than 1 host during their lifetime

Planarian

• Nonparasitic flatworm

• Glide over rocks, damp soil, and swim slowly through oceans

• Scavengers:– Feed on dead or decaying material

Planarian

• They also are predators towards animals smaller than they are

• Have eyespots– Function sort of like eyes but can not see

specific images

• Head has cells to pick up odors – Use smell to locate food

Planarian

• Feeds like a vacuum cleaner – Inserts a feeding tube into its food

• Sucks up partly digested food

• Distributed to body cells by diffusion – Only have 1 opening– Undigested food leaves through the feeding

tube

Roundworms

• Million roundworms live in each square meter of sand

• Live in moist environment

• Tiny and hard to see

• May be the most abundant animal on Earth

Roundworms

• Cylindrical body– Tiny strands of spaghetti

• Can be carnivores, herbivores, or parasites

• Hookworms are a roundworm parasite

Hookworm

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Roundworms

• Have a digestive system that is open at both ends

• Waste exits through the anus

• Having a one-way digestive system allows the worm to use its food efficiently and absorb more nutrients

Segmented Worms

• You can find them in your own backyard

• Leeches are parasitic segmented worms

• More closely related to crabs and snails

http://news.discovery.com/human/2010/11/12/leech-278x225.jpg

Segmented Worms

• Occupy nearly all environments

• Use burrows to hide from predators

• Sit-and-wait predators

Segmentation

• Bodies are made up on many linked sections called ___________– Segments

• Earthworms usually have more than 100 segments

• Some organs are repeated in most segments

Segmentation

• Ex:– Each segment has tubes that remove wastes– Reproductive organs are found in only certain

segments– Nerve cords and the digestive tube run the

whole length of the body

• 1 way digestive tract which means they have an anus

Closed Circulatory System

• Blood moves only within a connected network of tubes called blood vessels

• In an open system the blood leaves the circulatory system and sloshes inside the body

• A closed system can move the blood faster

Closed Circulatory System

• If you have a closed system you can be larger and more active– Blood carries

oxygen and food to cells

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Earthworms

• Earthworms scavenge for– Dead and decaying plant and animal remains

in the soil

• When it is damp they come out of their burrows– They only come out when it is damp because

their skin can’t dry out

Earthworms

• They mainly come out at night because they are safer from predators

• Obtain oxygen through the moisture on their skin

• Bristles on the segments help the worms move

Earthworms

• Benefit us:– Make the soil more fertile with their droppings

– Loosen soil when they tunnel

– Allow air, water, and roots to move through the soil when they tunnel