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

Assignment:

Sign up for an organ system. Every Student needs to pic a different system. This is worth 25 points and is due Thursday the 11th.

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

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

Observation of a Live Planarian

You will receive a small petri dish with a flatworm inside it. The flatworm is the freshwater planarian, also known as Dugesia. For more information on the planarian, check out this Article on the Planarian or read the related chapter in your textbook.

Prelab Questions

1. To what kingdom do planarians belong? ________________________ What phylum? __________________

2. What type of symmetry does this worm have?

3. Where do planarians live?

Observations and Experiments on the Flatworm

4. Observe your worm, using a microscope or hand lens. Sketch the planarian below. Label the eyespots. Label the anterior and posterior ends. Pay attention to detail on your sketch!

5. Measure your planarian. This operation is best performd by removing some of the water from the dish and waiting for the worm to stretch out. Measure the length of the worm in millimeters. (Always replace the water, you can use the dish lid to transfer water to and from the planarian environment.)

.................................................................... Length of Planarian _______

Write your length on the board and when all the lengths are down, determine the average planarian size. Average ___________

6. Observe the planarian for five minutes. Does the planarian seem active or passive? How does it move? Does it swim or creep? Where in the dish does it spend most of its time? Make a current in the water with a pipette. How does the planarian react? Fill out the table below.

7. Planarians actually display a handedness, being right or left handed. You can discover whether your worm is right or left handed by flipping the planarian over on its dorsal (back) and seeing which way it recovers. If it rolls to the right, it is right handed, if it rolls to the left, it is left handed. Do five trials to determine the handedness of your planarian.

8. Design an experiment to test the planarians reaction to light and dark. You will have flashlights and the room will be darkened for this part of the lab. Describe your experiment and be detailed enough that someone else could perform the exact same experiment. You can even use a numbered list to describe your procedure.

Conduct your experiment to determine whether the planarian prefers light or dark. Construct a data table.

Write your conclusions. Make sure you answer the question: Does the planarian prefer a light or dark environment and include your reasoning.

9. Drop a piece of food into the petri dish with the planarian. Observe the planarian's reactions. It may take a few minutes. How does it eat the food? Where is its mouth? Use the space below to write your observations.

What is the name of the tube used for feeding in the planarian?