Lab 6- Invertebrates Flashcards
List at least five characteristics that define animals and compare/contrast animals to plants and/or fungi.
1) are multicellular
2) are chemoheterorophic and obtain their nutrition usually by ingestion
3) move under their own power at some point in their life cycle
4) have cells that are eukaryotic. Their cells lack walls but have an extensive extracellular matrix
5) have unique tissue for impulse conduction (nerve cells) and movement (muscle cells)
6) can reproduce sexually but some of the simpler animals also reproduce asexually
Describe The number of tissue layers in the embryo.
a) all animals have tissues. IN the phylum porifera (sponges) the only tissue is the epithelial tissue covering the animal’s outer surface. The rest of the cells in sponges are not very specialized and not organized into tissues. Most body functions are carried out at the cellular level.
b) Tissue layers present in embryos
all animals other than sponges have tissues that are collections of specialized cells isolated from other tissues by membranous layers. The presence of tissues allows divisions of labour, with different tissues performing different functions.
some animals only have two tissue layers in thei embryos and are said to be diploblastic. Their embryos have an innner tissue layer, the endoderm and an outer layer the ectoderm ex. phylum cnidaria
most animals however, have 3 tissue layers in their embryos and are said to be tripoblastic. The third layer the mesoderm is sandwiched between the endoderm and the ectoderm.
describe Symmetry and cephalization.
Although some animals do not have symmetry (porifera) most are either bilaterally or radially symmetric
a) radial symmetric animals can be cut through the middle in many planes and still produce mirror images. That have top and a bottom, but no head or a tail, no front and back, no left and right (they are also dipoblastic) ex. phylum cnidaria
b) bilateral symmetric animals ahve only one plane in which they can vbe cut in two resulting in two parts that are mirror images of each other. They have a head and tail, a left and right, and a front (ventral) and back (dorsal) Most animal phyla fall into this clade. It should be noted that some animals in this clade have reverted back to some form of radial symmetry. For example adults are radial but larvae are bilateral
Animals showing bilateral symmetry are in the clade Bilateria. Such animals are also tripoblastic
Associated with the bilateral symmetry has been the evolutionary trend towards cephalization: the concentration of sensory organs in the anterior (front) end of the animal ( a head )
Describe: The presence or absence and type of coelom
Tripoblastic animals may be classified according to whether or not they have an internal body cavity between the digestive tract and the body wall. The scientific name for such a body cavity is a coelom. A coelom is fluid-filled and provides a space for organ developmet and the circulation of oxygen and nutrients. IN many soft-bodied animals it functions a hydrostatic skeleton.
a) acoelomates have no internal cavity, the body wall is solid
ex. Platyhelminthes
b) Pseudocoelomates posses a body cavity that develops between the endoderm and the mesoderm
ex. nematoda
c) Coelomates have a “true” coelom, a body cavity that develops within the mesoderm
ex. chordata
describe The type of embryological development
there are two distinct types of embryological development in animals
a) protostome development:
cleavage is spiral and determinate, with each cells development being set very early in development. The first opening (blastopore) becomes the mouth.
ex. annelida
b) Deuterostome development
cleavage is radial and indererminate, where early cells retain the capacity to develop into a complete embryo. the first opening becomes the anus and he second opening becomes the mouth.
ex. chordata
Explain the advantage of bilateral symmetry and cephalization
Locating and capturing food is particularly efficient when movement is directed by a distinctive head region and powered by the rest of the body
List the advantages of having a body cavity (i.e. a coelom).
• Acts as a “container ” for the internal organs.
• Suspends organs in fluid
• Provides cushioning, prevents injury
• Allows for free movement of organs
• Also used to circulate O2, dissolved nutrients.
• Serves as a hydrostatic skeleton that facilitates movement in some animals that don’t have
limbs. (earth worms)
Given specimens that you have observed in lab, state:
o How the organism carries out gas exchange (diffusion? organ?) and/or circulation (diffusion? circulatory system? If so, open or closed?).
o How the animal obtains nutrients (feeds) and/or if it has a digestive tract (if so, is it complete or incomplete?).
o How the organism moves.
o Features that distinguish the represented phylum from animals in other phyla.
answers are on the worksheet we handed in before the break
Define hydrostatic skeleton, exoskeleton, and endoskeleton
Hydrostatic skeleton or hydroskeleton: is a structure found in many cold-blooded organisms and soft-bodied animals consisting of a fluid-filled cavity, the coelom, surrounded by muscles. The pressure of the fluid and action of the surrounding circular, longitudinal, and/or helical muscles are used to change an organism’s shape and produce movement, such as burrowing or swimming. Some examples are soft bodied animals such as sea anemones and earthworms.
Exoskeleton: a rigid external covering for the body in some invertebrate animals, esp. arthropods, providing both support and protection.
Endoskeleton: an internal skeleton, such as the bony or cartilaginous skeleton of vertebrates.
State the evolutionary trend observed in the digestive tracts of animal phyla.
No digestive tracts—> incomplete digestive tract—> complete digestive tract
