Embedded Files
Animals
Animals originated more than 700 million years ago
-Our evidence for this is a fossilized hormone that is produced by sea sponges. The hormone is 710 million years old.
The first animals were sea sponges or something very similar to sea sponges
-Current evidence suggests that the first animals (sea sponges) evolved from a single celled eukaryotic organisms called choanoflagellates
Phyla Porifera (Pore bearer)
A sea sponge is barely an animal.
-The sponges cells act independently.
-The cells feed themselves
-Communication between the cells is week
-There are no organs
-No true tissue
Around 680 million years ago the first animals with true tissue evolved
Phyla Cnidaria
Cnidarians
-Sea Anemones
-Sea Jellies
-Coral
Cnidarian Characteristics
-Radial symmetry or Biradial
-Diploblastic Tissue level
-Gelatinous Mesoglea
-Nerve Net
-Cnidocytes
-Gastrovascular Cavity
What makes Cnidarians stand out is their cnidocytes
-Cnidocytes are stinging cells located on tentacles
-Cnidocytes discharge a harpoon like stinging structure called a nematocyst
Cnidarians have two body structures
-Polyp
-Medusa
-The polyp is a sessile structure that is attached to a surface and has the tentacles at the top like an anemone
-The medusa structure has the tentacles hanging like a sea jelly
Between 535 and 525 million years ago was the Cambrian period
-We refer to the Cambrian Explosion as a time when many new animals evolved in a very short time
-Out of the Cambrian Explosion we got Porifera, Cnidarians, Mullusks, Arthropods, and maybe even chordata.
In order to understand the evolution of complexity in organisms we will spend some time talking about body structure
Lets learn the parts...
Tissue
-Animal tissues are classified into 4 types
-Epithelial
-Connective
-Muscle
-Nervous
-Epithelial Tissue is basically any tissue that covers something or lines something
-Skin or stomach lining
-Connective Tissue supports and binds things together
-There are four major types of connective tissue
-Adipose Tissue - a type of loose connective tissue that stores lipids. Known as fat
-Cartilage - A hard yet flexible tissue used for support
-Like human ears or the whole skeleton of a shark
-Bone Cells - Made of calcium phosphate and calcium carbonate making it very hard
-Blood - a connective tissue in which fluid called plasma suspends special cells (blood cells)
-Muscle Tissue allows movement
-There are three kinds of muscle tissue
-Skeletal muscles are the ones associated with movement
-Smooth muscle has a turning motion. It is the type that moves food around and expands the bladder
-Cardiac muscles cause the heart beat
-Nervous tissue is for communication
-There are lots of types
-Neurons - Impulse conducting
-Neuroglia - Protection, support, and nourishment
-Peripheral glial cells - Form sheaths to protect the peripheral nervous system
Organ systems
Integumentary system
Skin, hair, nails
Nervous system
Brain, spinal cord, nerves
Endocrine system
Hormone-secreting glands (pituitary, thyroid, adrenals)
Skeletal system
Bones, cartilages
Muscular system
Skeletal muscles
Circulatory system
Heart, blood vessels, lymphatic vessels
Immune system
Bone marrow, lymphoid organs
Respiratory system
Lungs, Airways
Urinary system
Kidneys, ureters, urethra
Digestive system
Mouth, stomach, intestine, liver, gallbladder, pancreas
Reproductive system
Gonads, external genitalia, associated glans and ducts
Body symmetry
Animals come in three different types of symmetry
-Asymmetry - Has no symmetry like sea sponges
-Bilateral symmetry - The animals can be divided into right and left mirror images like humans
-Radial symmetry - The animal can be divided in anyway along the aboral oral axis and make a mirror image like sea jellies
Terms of direction
Aboral - The end opposite the mouth
Oral - The end containing the mouth
Anterior - The head end
Posterior - The tail end
Caudal - Toward the tail
Cephalic - Toward the head
Distal - Away from the point of attachment (Toes are distal to the knee)
Proximal - Toward the point of attachment (The hip is proximal to the knee)
Dorsal - The back of an animal
Ventral - The belly or underside of an animal
Inferior - Below a point
Superior - Above a point
Lateral - Away from the plane that divides a bilateral animal into a mirror image
Medial (Median) - On or near the plane that divides a bilateral animal into a mirror image
Diploblastic organization
-Diploblastic tissue organization is the simplest type of tissue organization
-There is basically only two tissue levels in a diploblastic animal
-The two layers are the
-Ectoderm
-Endoderm
-In between these two layers is a Mesoglea which sometimes has cells and sometimes does not
-The ectoderm gives rise to the epidermis and the endoderm gives rise to the gastrodermis
Sea Jellies are an example of a diploblastic animal
Triploblastic Organization
-Triploblastic organisms have an extra tissue layer called a Mesoderm
-The mesoderm gives rise to the organs
Coelom
-A coelom is the space between the mesoderm and the gut
-This space is where the organs rest
There are three types
-Acoelomate
-Psudocoelomate
-Coelomate
Page updated
Google Sites
Report abuse