saadia Archive

FURTHER PHYLOGENETIC CONSIDERATIONS IN AMPHIBIANS

FURTHER PHYLOGENETIC CONSIDERATIONS IN AMPHIBIANS There is a problem in amphibian phylogeny. This problem is the relationship among the three orders of modern amphibians. There are two hypotheses about the origin of amphihians: Monophyletic lineage Some zoologists place anurans, urodeles . and caecilians into

AMPHIBIANS IN PERIL

AMPHIBIANS IN PERIL Frogs and salandam are disappearing rapidly. We do not know the exact reasons of their disappearance. Some reasons are: 1. Local factors: Some local factors influence the amphibian populations. These factors are cutting of forests. It allows sunlight to reach at

EVOLUTIONARY PRESSURES IN AMPHIBIANS

EVOLUTIONARY PRESSURES IN AMPHIBIANS The lives of the most amphibians is divided into freshwater and land. Thus they show adaptations to both environments. The amphibians are supported by the buoyant of the water. They exchange gases with the water. They face the same osmoregulatory

SURVEY OF AMPHIBIANS

SURVEY OF AMPHIBIANS Amphibians occur on all continents except Antarctica. There are three orders of amphibians: Caudata, (salamanders), Anura, ( frogs and toads) and Gymnophiona (caecilians). ORDER CAUDATA (cauda, tail + Or. ara,  to bear) The characteristics are: 1. They possess a tail throughout

Amphibians Evolution

AMPHIBIANS EVOLUTIONARY PERSPECTIVE (amphibia, living a double life) Class Amphibia includes frogs. roads, salamanders and caecilians. Class name shows that amphibians move between water and land. They spend one stage or their life in water and another on land. Amphibians are tetrapods. Term tetrapod

OBJECTIVES OF THE FISHES – fisheries mcqs with answers

OBJECTIVES OF THE FISHES Multiple Choice Questions MCQs 1. Adaptive radiation in fishes started about number of million years ago: (a) 1200                  (b) 500                   (c) 1000             (d) 1500 2. Bony armor fishes are: Placoderms       (b) Ostracoderms      (c) Elasmobranchs      (d) None 3. The fish remained

SUBJECTIVE QUESTIONS OF THE FISHES

SUBJECTIVE QUESTIONS OF THE FISHES Describe evolutionary perspective of fishes. Describe phylogenetic relationships of fishes. Discuss whether evolution of fishes takes place in marine or fresh water environment. Give characters of Agnathans. Name its different classes with examples. What are ostraeoderms? What is their

Evolutionary Pressures in Fishes

EVOLUTIONARY PRESSURES The aquatic environments have physical characteristics. These characteristics are important selective forces for aquatic animals. Fishes have following adaptive characteristics: LOCOMOTION Water is dense. It makes movement through it difficult. It makes movement through it difficult. However, fishes uses less energy for