Test 6 - Complex Animals - Annelids

2025-07-29

What does annelus mean?

little ring

The three classes of annelids

oligochaeta, hirudinea, polycheata

examples of oligochaeta

earthworms

examples of hirudinea

leeches

examples of polychaeta

marine worms

Do annelids have a coelom? What does this entail.

Yes, body cavity w/ true organ systems and muscular layers

What organ systems do annelids have?

digestive, circulatory, nervous, excretory

What organ systems do annelids not have and what does it do instead?

respiratory, diffusion

What is diffusion? Why is it enough for small animals?

passive movement of molecules from an area of higher concentration to lower concentration, without using of energy.

• Small size, large SA relative to volume

• Thin body walls,

• Moist surfaces, O₂ and CO₂ dissolve easily in water

• Low oxygen demand, lower metabolic rates

What is metabolism and what does it tell you about an animal (high/low)?

sum of all chemical reactions in an organism that keep it alive, how it uses energy.

• e.g. Break down food to release energy (catabolism), build up tissues using energy (anabolism).

• High = uses energy quickly (small, active, endothermic), needs more O2 & food, fast digestion.

  • Low = opposite

Describe the thin, flexible, non-cellular outer layer covers the Annelid epidermis?

• made of collagen-like proteins secreted by epidermal cells

• prevents water loss

How are annelids segmented

sequence of departments by septa (walls between rooms)

How are annelid segments marked?

by annuli rings (in earthworms, each segment has one annulus)

How do annelids reproduce (sexual or asexual), and give examples.

• sexual, cross fertilization, copulates to mix gametes

  • Sperm exchanged between two hermaphroditic worms, and fertilization happens in a mucus cocoon secreted by the clitellum

• asexual, regeneration & fission

Are annelids hermaphroditic or dioecious?

hermaphroditic

What environments are annelids found in

terrestrial, freshwater, marine

Range of size for annelids

1mm - 3m

Parts of the earthworm digestive systems (7)

• one way tube

• mouth

• anus

• esophagus

• crop (storage between digestion)

• gizzard (grinds food)

• intestines

Does the earthworm have a closed or open circulatory system

closed circulatory system.

How many blood vessels do earthworms have, what are their names, and what do they do?

2, dorsal & ventral blood vessels circulate

How many hearts do earthworms have, and what do they do

5, pumps blood into 2 blood vessels

What do earthworms use to carry their oxygen in their cir

hemoglobin

Describe excretory system of earthworms

nephridia (primitive kidneys) that get rid of waste from blood

Describe the nervous system of earthworms

cephalization with primitive brain & ventral nerve cord

compare the closed circulatory system to open. (3 each)

Closed:

• Blood stays inside vessels (arteries, veins, capillaries)

• More efficient at transporting

• Higher pressure, faster circulation (tube)

Open:

• Blood (hemolymph) flows freely into body cavities, bathing organs directly

• Lower pressure, slower nutrient delivery

• Less efficient, but uses less energy

What does the circular muscle do in earthworms

contracts to make worm thinner/longer

What does the longitudinal muscle do in earthworms

contract to make worm shorter/thicker

Look at this image and memorize

Good

How are annelines ecologically important (8)

• base of many food chains

• houses parasites like Protozoa, Platyhelmenthes, & Nematodes

• aerate & mix soil (surface & mineral, through travel)

• constructive to mineralization & nutrient uptake by vegetation

• composts, turns dead organic matter into soil

• cycle nutrients & minerals through their casts (worm poop)

• increase nitrogen, phosphates & potach (potassium based) levels

• burrowing and keeping the soil structure open (aerating soil and providing a path for drainage)

Name all the parts of this earthworm and their functions.

• mouth: soil & organic matters, no teeth (uses muscular action to push soil and food into mouth)

• anus: exit

• clitellum: produces mucus for reproduction and cocoon for eggs

• brain: ganglion, controls sensory input & corrdinates movement

• heart: 5 aortic arches pumping blood thorugh closed circulatory system

• male reproductive organs: produce and release sperm

• nerve cord: trans nerve signals between ganglion & body segments

• blood vessel: dorsal & ventral vessals circulate

• digestive tube: absorbs nutrients, eliminates waste

• circular muscles: around segments, contracts to lengthen

• longitudinal muscles: contracts to shorten

• Setae: tiny bristles on each segment that anchor worm to soil

• nephridium: excretory organs in each segment that remove metabolic waste and maintain fluid/

How do many annelids and earthworms especially feed

detritus feeders

how many germ layers

3

what symmetry

bilateral

direct or indirect development in earthworms

direct