DEFINITIONS AND KEY POINTS FOR OBJECTIVES
saadiaDEFINITIONS AND KEY POINTS FOR OBJECTIVES TERMS DEFINITIONS Paedomorphosis Sexual maturity in a larval body form is called paedomorphosis. Zooids The two (or more) animals formed as a result of…
FURTHER PHYLOGENETIC CONSIDERATIONS
FURTHER PHYLOGENETIC CONSIDERATIONS There are different views about the evolution of platyhelminthes: Zoologists believe that the platyhelminthes body form is central to animal evolution. They believe that an ancestral flatworm…
PHYLUM GASTROTRICHA (Or. gastros, stomach i- trichos, hair)
PHYLUM GASTROTRICHA (Or. gastros, stomach i- trichos, hair) They have about live hundred free- living marine and freshwater species. They live in the space between bottom sediments. Their size is…
PHYLUM NEMERTEA
PHYLUM NEMERTEA There are nine hundred species of nemerteans. They are elongate, flattened worms. They are found in marine mud and sand. They have a long proboscis. Therefore, nemerteans are…
How is the vertebrate brain related to spinal cord?
rubabEvolution of the vertebrate nervous system included development of a single. tubular nerve cord above the notochord. During early evolution, the nerve cord underwent expansion, regional modification, and specialization into…
Describe nervous system in various invertebrate groups with special reference to the evolutionary trends.
Although no real nervous system is present in protozoa and sponges, coordination and reaction to external and internal stimuli such as, to light, temperature, chemicals etc do occur Only animals…
How is an action potential transmitted between neurons?
When an action potential passes down an axon to its terminal, it must cross a small gap, the synapse (Gr. synapsis, contact, union), separating it from another neuron or an…
What is saltatory conduction?
Saltatory Conduction is different means of speeding the propagation of action potentials has evolved in vertebrates. Many axons in vertebrate nervous systems are myelinated, that is, coated with insulating layers…
CLASS CESTOIDEA: THE TAPEWORMS
CLASS CESTOIDEA: THE TAPEWORMS It is the most highly specialized class of flatworms. The members of cestoidae are commonly called tapeworms. It has 3,500 species. All are endoparasites. They live…
Phases of action potential & role of gated ion channels
Stages / Phases of Action Potential: 1. All cells have a membrane potential; however, only certain kinds of cells, including neurons and muscle cells, have the ability to generate changes…