saadia Archive
SURVEY OF FISHES Debate on taxonomy of fishes is going on for many years. Modern cladistic analysis has revised he taxonomy of this group of vertebrates. (a) Traditional classification: The fishes are traditionally divided into super classes. This classification is based on the presence
THE FISHES VERTEBRATE SUCCESS IN WATER EVOLUTIONARY PERSPECTIVE Importance of water: Water is a buoyant medium. It resists rapid fluctuations in temperature. Water covers over 70% of the earth’s surface. Life began in water. The living tissues of the organism are mostly made up
OBJECTIVES OF HEMICHORDATA & CHORDATES Multiple Choice Questions MCQs 1. Which of the following is not a deutrostome? (a) Chordates (b) Hemichordates (c) Molluscs (d)Echinoderms 2.Acorn worms belongs to class: (a) Enteropneusta (b) Planctosphaeroidea (c) Pterobranchia (d) None 3. Planctosphaerara pelagica belongs to class:
SUBJECTIVE QUESTIONS OF HEMICHORDATA & CHORDATES 1.Describe evolutionary perspective of phylum Hemichordata. 2. Write phylogenetic relationships of Hemichordates, Echinoderms and Chordates. 3. Give general characteristics of phylum Hemichordata. 4. Describe classification of phylum chordata up to class. 5. Give classification of Chordates up to
DEFINITIONS & KEY POINTS FOR OBJECTIVES OF HEMICHORDATA & CHORDATES TERMS DEFINITIONS Tunicates Tunicates and a small group of fishlike cephalochordates lack a vertebral column. Deutrosomes The animals in which blastopore are changed into anus and mouth is arised as a separate opening
FURTHER PHYLOGENETIC CONSIDERATIONS Relationship between Hemichordates and Chordates It is difficult to establish evolutionary relationships between the hemichordates and chordates. Two common characteristics are present between these groups: 1. Dorsal tubular nerve cord. 2. Pharyngeal slits of hemichordates. These two characteristics are the evidence
PHYLUM CHORDATA (chorda, cord) Phylum Chordata has about 45,000. Its members are very successful at adapting in aquatic and terrestrial environments. Characteristics of the phylum Chordata are: 1. They are bilaterally symmetrical deuterostomes animals. 2. Four unique characteristics present at some stage in development.
PHYLUM HEMICHORDATA (hemi, half + chorda, cord) The phylum Hemichordata includes the acorn worms (class Enteropneusta) and the pterobranchs (class Pterobranchia. Members of both classes live in or on marine sediments. Characteristics of the phylum Hemichordata are: 1. They are marine deutrostome animals. 2.
CLASSIFICATION OF HEMICHORDATA & CHORDATA Phylum Hemichordata Hemichordates are widely distributed in shallow, marine and tropical waters. They are present in deep and cold waters. They have soft and wormlike bodies. They have epidermal nervous system. Most hemichordates have pharyngeal slits. They have three
HEMICHORDATA & CHORDATES EVOLUTIONARY PERSPECTIVE Hemichordata have some most familiar animals. We are familiar with them because we are members of phylum Chordata. Other members of these phyla are much less familiar. Some hemichordates form coiled castings (sand, mud, and excrement) at the opening
