Lecture 7: The Evolution and Diversity of Animals Flashcards
What is the nutritional mode of animals? describe it
Animals are chemoheterotrophic. This means, they must consume other organisms to obtain an energy source and an organic carbon source- since they cannot convert inorganic carbon into organic carbon.
How do animals differ in structural complexity from animal-like protists?
While both animals and animal-like protists are eukaryotic, animals are multicellular whereas animal-like protists are usually unicellular or sometimes colonial.
What is the relationship between animals and modern choanoflagellates?
Animals and modern choanoflagellates are sister taxa, meaning they share a common ancestor and are closely related.
Approximately when did the first animals evolve?
At least 710 million years ago
Describe the morphological and genetic evidence that supports choanoflagellates are the closest living relatives of animals?
Morphologically, the cells of choanoflagellates and the collar cells of sponges are nearly identical. As well, very early animals (Ediacaran) resemble extant sponges, cnidarians, and molluscs.
Genetically, DNA sequencing has determined the two as sister taxa, meaning they are both extant and share a common ancestor. Evidence for this are the genes for certain proteins have been found only in animals and choanoflagellates.
What are the 3 embryonic germ layers that can be present in animals? In order from the outside to the inside of the organism
the outermost layer is the ectoderm
the innermost layer is the endoderm
in bilaterally symmetrical animals, there is a middle layer called the mesoderm
What is a coelom? How is it different from the cavity that forms the digestive system?
A coelom is a body cavity located between the digestive tract and the outer body wall. A coelom forms from the mesoderm germ layer, meaning it is only present in triploblastic animals. The tissues that coat the coelom form and connect the structures that suspend organs.
Whereas, the cavity that forms the digestive system is formed from the endoderm germ layer, meaning that all animals have this cavity and therefore, a digestive tract.
What is an endoskeleton? Give an example
the hardened INTERNAL skeleton within the soft tissues of an animal.
For example, the cartilage and bone skeleton of mammals.
What is an exoskeleton? Give an example
A non-living, hard cover of deposits on an animal’s EXTERIOR surface.
For example, the calcium carbonate shell of most molluscs or the cuticle (jointed exoskeleton) of an insect.
What are the major differences between an endoskeleton and an exoskeleton?
One major difference between an endoskeleton and an exoskeleton is the location of the skeleton. The endoskeleton is on the inside of the animal, whereas the exoskeleton is on the outside.
Define what a hydrostatic skeleton is and describe one major advantage of this kind of skeleton?
A hydrostatic skeleton is a skeleton made up of fluid held under pressure in a closed body compartment.
A major advantage of these skeletons are that the animal has control over their body form and movements because they can use muscles to change the shape of the fluid-filled compartments. Very beneficial for aquatic environments, and burrowing or crawling animals.
What is the gastrovascular cavity?
A body cavity with a SINGLE opening in some animals (like cnidarians and flatworms) that functions in digestions and distribution of nutrients
Define what body plans are in animals? What are the 5 plans?
Body plans are a set of morphological and developmental traits integrated in the entire living organism. These traits can be used to distinguish different animal phyla.
- symmetry
- tissue origin
- digestive cavity
- body cavity
- skeleton
Define radial symmetry
Animals that are radially symmetrical can be cut into 4 equal pieces in order to fit their sessile lifestyles. Having the same features on all sides of the animal allows it to meet its environment from any direction with equal ability.
Define bilateral symmetry
animals that are bilaterally symmetrical can only be cut into 2 equal parts down the middle creating a left and right side. These animals also have a top (dorsal) and bottom (ventral) side and a front (anterior) and back (posterior) end. The anterior of an animal is usually where their central nervous system (brain) is, which allows them to coordinate complex movements such as walking, flying, swimming, etc. in their mobile lifestyles.
Which animal phyla are radially symmetrical animal?
cnidaria (jellies and hydras) adult echinodermata (sea stars, brittle stars, etc.)
Which animal phyla are bilaterally symmetrical animal?
annelida arthropoda chordata larval echinodermata mollusca nematoda platyhelminthes
Describe tissues in animals (in terms of body complexity)
True tissues are collections of specialized cells that function as a unit and are separated from other tissues by membraneous layers.
What are germ layers?
As it develops, the embryo of an animal becomes layered. Through development, each layer forms various tissues and organs of the body.
Describe the ectoderm
The ectoderm is the outermost germ layer that covers the exterior of the embryo which eventually will develop into the outer covering of the animal and for some species, it will become the central nervous system.
Describe the mesoderm
The mesoderm is the possible middle germ layer that will only form in bilaterally symmetrical animals. This germ layer forms between the ectoderm and the endoderm. It will develop into the muscles and most organs between the digestive tract and the outer covering of the animal.
