Invertebrates

What is an Animal?• We take it for granted that

animals are things that are fuzzy, furry and we can pet

• However to really understand what animals are, we have to have a broad definition of animals and an open mind

• Not all animals fit the 3rd grade idea of an animal

What is an Animal?• Animals are…

– Multicellular– Heterotrophs– Eukaryotic– Obtain nutrients through

ingestion• Multicellular – Many Cells• Heterotrophic – Other

Feeding• Eukaryotic – True Nut• Ingestion – Process of

Eating

What is an Animal?

• Also animals have a few other fun features– Distinctive cell

organelles– No cell walls– Held together by

collagen• All of these factors are

things that make animals unique

Animal Development

• The process of reproduction is similar to most animals as well

• Adults produce the gametes eggs or sperm through meiosis

• Eggs and sperm combine to create a zygote

• A zygote is a single cell created from the fusion of egg and sperm

Animal Development

• The zygote starts to undergo mitosis

• This happens rapidly and the number of cells starts to grow

• The cells then form a blastula

• A blastula is a ball of cells that is typically hollow

Animal Development

• Once the blastula has formed one of the sides starts to fold into itself

• When this happens the group of cells is called a gastrula

• The inner folds are called the endoderm

• They will form the digestive tract

Animal Development

• The cells that remain on the outer layer are called the endoderm

• They will eventually form the outer coverings of the animal

• They can also form some nervous organs

Animal Development

• The cells that are trapped in between the two layers are called the mesoderm

• These will form most of the internal organs of the animal

Animal Development• After the gastrula stage,

many animals develop to adults

• However not all animals are the same

• Some animals develop into a larval stage

• These animals will have to undergo metamorphosis later in life to reach an adult form

Body Plans

• Animals can be characterized by their body plans

• This means the makeup and location of their major parts, organs and brain

• Based on how organisms are laid out, we can tell a large amount about their history

Body Plans

• Symmetry plays a portent role in describing body plans

• Symmetry is a mathematical patterned self similarity

• Types of symmetry are important to understanding body plans

Body Plans• Radial symmetry is when

an organism is symmetric on a central body part

• All parts would be symmetrical if you used a pizza cutter

• Bilateral symmetry is when an organism’s halves are symmetrical

• All parts would be symmetrical if you used a buzzsaw

Body Plans• To define symmetry we

have to define the surfaces of an organism

• Anterior – Refers to an organisms head

• Posterior – Refers to an organisms tail (end)

• Dorsal– Refers to an organisms back

• Ventral – Refers to an organisms bottom (stomach)

Space – The Biological Frontier

• Take your hand and poke your partner’s (or your own if they object) belly

• What do you feel?• Is there a strong muscle

that goes from ventral to dorsal?

• What makes up that area?

Space – The Biological Frontier

• Organisms can have a body cavity… or not

• A body cavity is a fluid filled space between the outer digestive tract and the body wall

• Not every organism has a body cavity

Space – The Biological Frontier

• If there is a fluid filled space between the body wall and the inner digestive tract it is called a hydrostatic skeleton

• This enables a greater range of movement for the organism and cushions and protects the inner organs

Taxonomy • Once you understand

how organisms are built and develop we can define which ones are related

• Remember, a biological family tree is called a phylogenetic tree

Taxonomy

• Today we will be studying the different groupings of invertebrates

• Invertebrates lack a spinal column

• This does not limit their complex nature or their role in the environment

Sponges

• Sponges are organisms that have a simple porous body

• Considered the most simple organisms

• Contain no muscles or nerves

• Some are radially symmetric, however most have no major body plan

Sponges

• https://www.youtube.com/watch?v=BW05vMziy2o

Cnidarians• One of the oldest

invertebrates• Includes hydras, sea

anemones, corals and jellies (aka jellyfish)

• They have radial symmetry

• They are all carnivores• They use complex

nematocysts that sting prey

Cnidarians

• They have two major body types

• A polyp is fixed on one end with extending tentacles

• A medusa is a free moving form of the cnidarian that can move with or against the tide

Cnidarians

• http://shapeoflife.org/video/behavior/cnidarians-anemone-catches-goby

Platyhelminthes

• This consists of the flatworms– They are worms… that

are flat• Have a gastrointestinal

system with only one opening

• Due to their nature they need to be in water or damp envrionments

Platyhelminthes

• Free-living Flatworms live under rocks and have light sensitive eyecups

• Flukes live as parasites and can utilize multiple hosts

• Tapeworms are intestinal parasites that have no digestive tract

• http://videos.howstuffworks.com/discovery/42160-monsters-inside-me-japanese-lung-fluke-video.htm

• http://www.mirror.co.uk/tv/tv-news/infected-video-bbc-presenter-infected-3094743

Nematodes• Nematodes are also called

roundworms– This is because they are

round… and worms• They have bilateral

symmetry and they have a false body cavity

• They have a mouth at the blunt end of the body

• They also have a tough outer coat called a cuticle

Nematodes

• Nematodes are the first organisms that have a one way digestive tract

• Many nematodes have a function as detritus feeders

• Some nematodes are parasites and can be dangerous

Nematodes• Has a true body cavity• They have an open

circulatory system• This means that organs are

bathed directly in blood• Their body has one small

brain with nerve clusters in each segment

• Their body has a large pumping organ in front and behind the body

Video

• A real life heartworm extraction

• Warning (Not for everyone)

• https://www.youtube.com/watch?v=phCod-0tfkE

Annelids• Annelids are segmented

worms– This means they are worms …

that have segments• Its body is segmented into a

region of repeating parts• Each part is designed to

function and move on its own

• Greatly increases the flexibility and speed of the organism

Annelids• Earthworms are the most

commonly found in damp soils

• The polychaetes are mostly marine and they are distinct for their “hairy” and feathery appearance

• Leeches are carnivores or parasites that are mostly in freshwater, salt water or live in trees

Molluscs• Molluscs are composed of

organisms that have a soft body, but most have a hard shell

• Snails, slugs, oysters, clams, octopus, squids and cuttlefish are all molluscs

• This really large and wide range of organisms is all in the same family

• Most only have a few common features, but differ greatly

Molluscs

• The three main parts of the mollusc are…

• A muscular foot which aids movement

• A section of visceral mass which contains most organs

• A mantle which is a fold of tissue that secretes a shell

Molluscs• The gastropods are the

largest group of molluscs– Gastro (belly) and pod (foot)

• These organisms mostly have spiraled mantles that create spiraled shells

• The bivalves are composed of clams, muscles and oysters– Bi (two) and valva (hinged

door)• They often live on

underground structures or in sediments

Molluscs

• Cephalopods are adapted to be fast and agile predators– Kephale (head) pod (foot)

• They have a small internal shell or it is absent

• They have a beak that is used for tearing apart food

Arthropods

• Over a million species of arthropods exist

• This makes them the most species successful animals in the world

• There are over 10^18 arthropods on the earth

• That is over a billion billion arthropods on the earth

Arthropods

• Arthropods have a few key features

• Arthropods have an exoskeleton that protects them

• Arthropods have segments of a head, thorax and abdomen

• Arthropods also have jointed appendages

Arthropods

• Chelicerates are organisms that live in the ocean

• It only has one member, the horseshoe crab

• It is considered a living fossil

Arthropods

• Millipedes ad Centipedes have many segments

• Centipedes have carnivores that have poison claws and one pair of legs per segment

• Millipedes have two legs per body segment

Arthropods

• Crustaceans are nearly all aquatic

• Lobsters, crabs, shrimp and crayfish are easy to identify

• However barnacles find themselves in this group as well

Arthropods• Insects are by far the

largest of the arthropod group

• They make up large number of the species that make up the earth

• They undergo multiple life stages with most insects undergoing a complete metamorphosis

• This means they have a larva, pupa and adult life stage