Download Animals – Invertebrates Part 1

Animals – Invertebrates Part 1
 Animals are the most 
o Animals range in size from 
o Animals are found nearly 
o All animals share a unique set of derived characters:
 Animal cells are 
 Three-stranded protein
 Found in 
 Animals are 
 Diploid parents produce 
 Do not have 
o Most animals have 
 Hox genes are 
 Hox genes 
 A hox gene mutation leads to the development of 
 Each animal phylum has a 
o Vertebrates have an 
o Invertebrates do not have 
o Invertebrates encompass 
o Differences in body plan results from 


Hox genes tell embryonic cells 
Mutations in hox genes lead to 
 Animals are grouped using three criteria:
1) Body plan symmetry
2) Tissue layers
3) Developmental patterns
o There are 2 types of body plan symmetry:
 Bilateral symmetry 
 Radial symmetry 
o Bilateral animals have 
1) Ectoderm 
2) Endoderm 
3) Mesoderm 
o Radial animals have 
1) Ectoderm
2) Endoderm
 Animals are divided into 2 major groups:
o Protostomes 
 Protosomes include 
o Deuterostomes 
 Deuterostomes include 
o Gut cavity formation:
 In protostomes 
 In deuterostomes 
o Cleavage pattern:
 In most protostomes early cell division leads to an eight-celled embryo
twisted in arrangement called 
 In deuterostomes, cells divide into eight-celled embryos with cells that are
lined up atop the other in an arrangement called 
 Phylum Porifera: Sponges have 
o Sponges are the most 
 570 million year old fossils
 Closely related to a 
o Sponges share common characteristics:
 Sessile 
 Reproduce both 
 They are 
o Sponges have several types of specialized cells:
 Pinacocytes 
 Choanocytes 
 Cells have flagella surrounded by a collar of tiny hairlike structures
called 


These cells pull water through the sponge by beating their flagella 
Ameobocytes 


They 
Transport 
 Phylum Cnidaria: Cnidarians are the 
o Cnidarians have 2 body forms:
 Polyps 

Medusas 
o Cnidarians reproduce both 
 Polyps reproduce asexually by 

Medusa reproduce sexually by 
 Fertilized egg develops into a free-swimming larva called a 
 The planula then develops into the 
 Many cnidarian species 
o Cnidarians are made up of 

Outer tissue layer has 3 cell types:
 Contracting cells 

Nerve cells 

Cnidocytes 
o Found all over a cnidarian’s body but 
o A nematocyst is a stinging structure found in both sea
anemones & jellyfish 

Gastrovascular cavity 
 Secretes 
 Also moves 
o The four major cnidarian classes are defined by 
1) Anthozoans 
2) Hydrozoans 
3) Scyphozoans 
4) Cubozoans 
 Phylum Platyhelminthes: Flatworms are 
o Flatworms have a 
o Flatworm’s shape is the direct result of having 
o They can only move oxygen to their cells by 
o There are three classes of flatworms:
1) Planarians 
 Have a 

Mouth is on ventral surface instead of on its 

A muscular tube called 
2) Flukes 
 Have a mouth with a pharynx that opens into 
 They are found in both 
 Tapeworms 
 They have a small head with 

Have no gut, instead they absorb nutrients from 

Adult tapeworm’s body is made up of segments containing 

When segments fill with fertilized eggs 
 Phylum Mollusca: Mollusks are 
o A complete digestive tract has two openings 
o Mollusks share at least one of three features:
1) Radula 
2) Mantle 
3) Ctenidia 
 In water mollusks it is 

In land mollusks 
o Mollusks have a heart and an open circulatory system 

Mollusks have a hemocoel 
o There are 7 classes of mollusks, but the majority of species are found in within
these 3 classes:.
1) Gastropods 
 Includes over 
 Live in both 
 Can be 
2) Pelecypods (aka bivalves) 
 Have a 
 Most are 
3) Cephalopods 
 Have a well developed 
 They are 
o Mollusks use a variety of 
 Most strategies involve 
 Some are hermaphrodites 

Reproduction involves 
 Phylum Annelida: Annelids have 
o Segmentation refers to the 
o Annelids have a closed circulatory system 
o The coelom is a 
 It is divided by partitions called 
 Fluid inside the coelom acts as a 
o Annelid Diet:
 Most eat 
 Some feed on 
o Annelid Reproduction:
 Asexual reproduction 

Sexual reproduction 
 Some species are hermaphrodites
 Some species have separate male & females
o There are three groups of annelids:
 Earthworms
 Marine worms
 Leeches
 Phylum Nematoda: Roundworms (nematodes) 
o They are protostomes with bilateral symmetry
o They are 
o Roundworms have a tough outer skeleton called a 
 Made of 
 Must be shed to 
o Roundworms have a 
o They reproduce 
 Some give 
 In most 
o Many roundworms are 
 Hookworms 

Pinworms 

Guinea worms 