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Live on the sea floor

Have porous bodies (no specialized tissues)

Characterized by special cells called choanocytes

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Body Plan:

Large sac with holes throughout the sides

Water is drawn into a large central cavity called the spongocoel and let out through the large hole on the top, called the osculum.

Currents are formed and food is trapped by flagellated cells call Choanocytes which line the spongocoel (also called Collar Cells)

Amebocytes wander throughout the inner cells transporting nutrients and form spicules for support

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Sponges are hermaphrodites

Male and female gametes are formed

Male gametes disperse into the water column and female gametes stay inside the organism

Male gametes will fertilize the female gametes and a larvae is formed

Larvae are pelagic and swim to a new site to start a new organism

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Have Radial Symmetry

Diploblastic

Gastrovascular Cavity: body plan that is made up of a sac within a sac

Cnidocysts (used to catch food)

Carnivorous - use their tenticles to push food into their gastrovascular cavity

Use Nematocysts to inject poison into their prey, inhibiting or killing them

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Polyps:

Sessile in location, these body types will sit and wait for prey to come by (Hydras and anemones)

Medusas:

Flattened down mouth versions and passively drift with the current (Sea Jellies)

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All are capable of sexual reproduction although many do most of their reproduction asexually

Polyps produce asexually and new individuals or "clones" are created from new buds of the parent polyp - once the bud is big enough it breaks off as a new polyp

Many are hermaphrodites

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Examples: Snails, Slugs, Clams, Mussels, Octopi, and Squid

Soft-bodied, some contained within shells

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Mantle

Secretes the shell

Visceral Mass

Most of the internal organs are located here, except for the gills and anus

Muscular Foot

Used for locomotion (movement)

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Mollusks use sexual reproduction to pass on there genes

usually a male and a female with the exception of some snails that are hermaphroditic

Some organisms such as oysters change there sex many time throughout their life

in aquatic environments the most common form of fertilization is external,  whereas fertilization in terrestrial snails is internal.

The diverse nature of this phylum is shown also in the many different methods of reproduction

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Kingdom Animalia: Phylum Mollusca | iKen | iKen App | iKen Edu

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Bilaterally symmetrical

Range in size from much less than 1 millimeter to more than 3 meters

Body divided into segments by transverse rings, or annulations

Annelids include more than 9,000 species among three classes

Most live in the ocean where they either float, burrow, wander on the bottom, or live in self-constructed tubes

Three classes:

Marine worms (Polychaeta) which are divided into free-moving, tube-dwelling forms

Earthworms (Oligochaeta)

Leeches (Hirudinea)

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Body is divided into segments by transverse rings

Almost all annelids have a fluid-filled cavity between the outer body wall and the gut, referred to as a coelom

Palps, antennae, eyes, statocysts, nuchal organs, and lateral organs help with sensory function

Coelom

used as a storage area for gametes and acts as a hydrostatic skeleton for locomotion

some leeches and small polychaetes have little or no coelomic space

Body Wall

Body covered by an external cuticle that is never shed or molted

A layer of circular muscle beneath the epidermis forms a nearly continuous sheath around the body

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Sexual or Asexual

Asexual reproduction is by fragmentation, budding, or fission

Among the sexually reproducing annelids hermaphrodites are common, but most species have separate sexes

Fertilized eggs of marine annelids usually develop into free-swimming larvae

Eggs of terrestrial forms are enclosed in cocoons and hatch as mini versions of the adults

Ability to regenerate lost body parts is highly developed in many polychaetes and digochaetes

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Complex Animals: Annelids & Arthropods - CrashCourse Biology #23

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Known as round worms

Bilaterally symmetrical

Unsegmented

Pseudocoelomates (do not have a full sized body cavity)

Simple digestive system

Lack a circulatory system

Tough outer coat

Many are parasites to plants and animals

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Although there is diversity within the life cycles of different nematodes, all follow the same basic pattern of growth and reproduction

Seven stages of the life cycle - egg, four larval stages, two adult stages

Sexual reproduction is initiated by adult females that have attached themselves to a host organism

The female lays eggs that are passed by the host to the external environment where the eggs then pass through three developmental stages before becoming larvae

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Three key features: Jointed appendages, Hard Exoskeleton, Body segmentation

Epidermis produces a segmented, jointed, and hardened chitinous exoskeleton with musculature between individual joints of appendages

Arthropoda includes crustaceans, insects, and chelicerates

Chelicerates: primarily terrestrial, includes horseshoe crabs and sea spiders

Crustaceans: marine and freshwater, absent from land

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Segmented bodies with some or all of the segments bearing jointed appendages

All have a chitinous, jointed exoskeleton

Simple eyes - light sensitive cells share a common lens

Compound eyes - thousands of closely packed units called ommatidia

Digestive System

Most arthropods have three main regions: foregut, midgut, and hindgut

Respiration and Circulatory System

Extensive surface areas are needed to supply the large oxygen demands of most arthropods (this is why gills are so large) - gills can occur both inside and outside of the carapace

Open circulatory system as in molluscs - hearts vary in structure

Blood is pumped into empty spaces bathing the tissues in blood

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1. Life starts as an egg

2. Nauplius

3. Protozoea

4. Mysis

5. Postilarval stage

6. Adult

With few exceptions, sexes are separate

sperm are commonly transferred to the female within sealed packets known as spermatophores

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Complex Animals: Annelids & Arthropods - CrashCourse Biology #23

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Radial symmetry

Exoskeleton of Calcium Carbonate

Water vascular system with tube feet for movement

Echinodermata are all marine, triploblastic, unsegmented coelomates

What sets them apart:

Pentagonal symmetry (bilateral in larvae)

Calcite spicules embedded in the skin, often partly fused

Tube feet

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Water vascular system

Complex system of water-filled canals

Extensions of tubed feet

Modification of the coelom

Ciliated internally

Madreporite serve to replace water lost from the water vascular system and equalize pressure

Tube Feet

Extensions of the canal system

Usually emerge through openings in skeletal ossicles

permit exchange of respiratory gases and nitrogenous waste

sensory functions

Nervous Sytem

Echinoderms have a diffuse nervous system with no "brain"

Nerve ring that encircles the mouth

Radial nerves that extend to each arm

Coordinate the functions of tube feet

Nerve net that coordinates the function of the body wall

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Sexes are separate, and discharge gametes into the sea water in response to chemo-stimulus of other gametes

Gonads can be large - and can be eaten as a delicacy

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Bilateral symmetry

Well-developed coelom

Ventral heart

Complete digestive tract

Endoskeleton (bone or cartilage or both)

Phylum Chordata Includes:

1. Invertebrate Chordates

Subphylum Urochordata

Subphylum Cephalochordata

2. Vertebrate Chordates

Subphylum Vertebrata

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Notochord:

Semi-rigid rod-like structure

Present at some times during development

Made of cartilage

Functions: stiffening, axis for muscle attachment

Hollow Dorsal Nerve Cord

Anterior end is brain

Is spinal chord in vertebrates

Pharyngeal Gill Slits or Pouches

Location: where pharynx will be

Present at some time during life cycle

Post - Anal Tail

Function: propulsion

Very good for swimming

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Urochordata

Tunicates and Sea Squirts

Marine bottom dwellers

Sessile adults with a leathery tunic

Larvae possess all 4 chordate trademarks

Cephalochordata

Lancelets (Amphioxus)

Marine

Fish-like shape, pointed at both ends

Silver in color

Small

Closed circulatory system

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Known as Flatworms or Tapeworms

Acoelomates

Triploblastic

Have a sac body plan

Flatworms have a single opening

Tapeworms do not have a digestive tract

Tapeworms

Parasitic

Live in vertebrates

Absorb nutrients directly from the host

Trubularians

Inhabit freshwater streams and marine type environments

Scavengers and carnivores

Flukes (Trematoda)

Parasites

Life cycle integrates asexual and sexual reproduction

Planarians

Lack organs for gas exchange and circulation

Move by cilia located on their ventral surface

More complex nervous system (able to change behavior to stimulus)

Have two eyespots and lateral slits used for smell

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Lack organs for gas exchange and circulation

Move by cilia located on their ventral surface

More complex nervous system (able to change behavior to stimulus)

Have eye spots and lateral slits used for smell

Sac body plan

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Life cycle integrates asexual and sexual reproduction

Asexual reproduction through regeneration

Sexual reproduction except for hermaphrodites