- Lab 1
During labs when we examine different Phyla of animals, we will use a set of tables to help compare and contrast them. The tables are constructed with the different Phyla (groups of organisms) in rows and characteristics in columns. The characteristics refer to morphological, developmental, and physiological traits. Some will be very easy to understand and you may already be familiar with them. Other will be new to you and we will go over them in lecture.
Animal Characteristics Chart 1
Animal
Characteristics Chart 2
Microscope care and use:
Below you will find
a link to a document on how to use the dissecting microscopes in Bio
225. You should download this file, open it with MS Word, print
it out, and bring it with you to
class. Learning how to use a microscope properly is a very
important skill for all biologists and will help you in future
classes. Two basic rules not included in the Swift
document: Never slide a
microscope
(it is very bad for it). Always adjust
the fine focus when you are looking at a specimen (It makes sure
the microscope is adjusted for your eyes and helps you get a clearer
view of what you are looking at).
Kingdom Animalia: a group of multicellular, eukaryotic, heterotrophic organisms. Members of the kingdom Animalia evolved from a common ancestor that would have been similar to the current choanoflagellate protistans (Hickman et al., 2008 fig. 11-18: note that Hickman refers to this group as Protizoans). Members of Kingdom Protista are unicellular eukaryotes but often live in aggregates, called colonies. WIthin the colony, some cells can be specialized to perform certain roles (e.g., collect food, provide protection). Over long periods of time the different types of cells become dependent on each other and multicellularity develops. The difference between colonial organisms and multicellular individuals is that the cells in a multicellular organism can not survive on their own, they are dependent on the other cells in the individual to live.
The first group of organisms we will examine are separated from other animals because they are weakly multicellular. Although sponges are organisms made of many cell types that perform different tasks to help keep the individual alive, the cells can survive independent of each other for extended periods of time. Sponges have no tissues, which are layers of cell of the same type that work together to perform a function.
Phylum Porifera: [pore bearer] sponges. (Hickman et al., chapter 12)Sponges are aquatic organisms. Most sponges occur in marine habitats although one freshwater family is found in streams of Kentucky. The body is classified as having no symmetry, or being radially symmetrical.
While no true tissues are present, there are different body layers. The outer layer of the body is covered by flat cells called Pinacocytes. Scattered across the surface of the sponge are tube shaped cells (Porocytes) which allow water to flow into the sponges body. The water, and all the algea and organic matter carried with it, then enters to spongocoel where Choanocytes attach onto the food. The spongocoel is a central chamber lined by Choanocytes.
Sponges feed by intracellular digestion where the breakdown of food happens inside of individual cells. The choanocytes, also called collar cells, are cells specialized for feeding. Choanocytes feed using a flagellum that create a water current past a mucus covered collar. As the water flows past the collar, algea and small bits of organic matter stick to the mucus. The mucus is then taken inside the animals cytoplasm by phagocytosis and the food particles are broken down.
Between the choanocytes and pinacocytes is an acellular layer called the mesohyl. The mesohyl is composed of a matrix of protein, sometimes with spicules (spines of calcium carbonate or silica) and spongin (an elastic protein). The material for the spicule is constructed inside Sclerocytes and when the cell dies the spine is left behind. Archaeocytes are cells that travel thoughout the body transporting materials.
Sponges reproduce sexually and asexually.
Specialized cells present:
outer covering
Pinacocytes
- flat platelike cells that cover the
outer surface.
Porocytes -
cells that form openings, through which
water is drawn into the
sponge.
middle area
Archaeocytes
- cells that travel through the mesophyl
performing various tasks. Sclerocytes - cells that form
spicules.
Choanocytes
(collar cells) - cells that line the
inner cavities of the sponge and collect food.
The Classes of Porifera are based on the type of spicules produced and body organization.
| Classes of Porifera: |
| Class Calcarea - spicules of calcium;small, shallow ocean forms with a simple bodyplan. |
| Class Hexactinellida - glass sponges; 6-ray silicon spicules make a rigid framework on which the live cells live; deep ocean forms. |
| Class Demospongiae -
when present, the spicules are made of silica and simple, Spongin
makes these animals "squeezable". 95% of all sponges; all depths
of oceans; 150 freshwater forms. Body plan is always complex,
with no well defined spongocoel. |