Amphibians Chapter 40 (798-814) Chapter 40 Amphibians

Objective 40.1 Describe three preadaptations involved in the transition from aquatic to terrestrial life Describe two similarities between amphibians and lobe-finned fishes List five characteristics of living amphibians Name the three orders of living amphibians and give an example of each Chapter 40 Amphibians

Origin and evolution of amphibians About 360 million years ago, amphibians became the first vertebrates to live on land. The name amphibian comes from the Greek word meaning “double” and “life” and reflects the fact that many amphibians spend part of their life on land and part in water. Chapter 40 Amphibians

Adaptation to land Most likely evolved from lobe-finned fishes Preadaptatins are adaptations in an ancestral group that allow a shift to new functions which are later favored by natural selection Fins had bone structure to walk as legs Modified pouches in digestive track  lungs Chapter 40 Amphibians

Chapter 40 Amphibians

Characteristics of early amphibians Skull and vertebra column, bones in fin and (similar) Scarcopterygian- extinct lobe-finned fish 360million years fossil record Had 4 strong limbs Gills, teeth, lateral lines Most likely spent most time in water Chapter 40 Amphibians

Diversification of amphibians Devonian period and carboniferous period amphibians split into 2 main evolutionary lines One modern amphibians Ancestors of reptiles 4500 species of amphibians 3 orders of amphibians O. Anura – frogs and toads (3900 species) O. Caudata- salamanders (400 species) O. Gymnophiona – caecilians (legless tropical) Chapter 40 Amphibians

Chapter 40 Amphibians

Modern Amphibians Aquatic larval to terrestrial adult (metamorphosis) Moist thick skin with no scales Feet- lack claws, webbed Gills, lungs, skin in respiration Eggs lack muticellular membranes or shells Eggs laid in water- external fertilization Chapter 40 Amphibians

Objective 40.2 Relate the structure of amphibians skin to the types of habitats in which amphibians can survive Identify three adaptations for the life on land shown by the skeleton of a frog Sequence the flow of blood through an amphibian’s heart Describe the digestive/ excretory systems Discuss the nervous system Chapter 40 Amphibians

Characteristics of amphibians As you have already seen, terrestrial vertebrates face challenges that are far different from those faced by aquatic vertebrates. In this section you will learn about some of the ways amphibians meet the challenges of living on land. Chapter 40 Amphibians

skin Two important functions Respiration Protection Moist, permeable to gases and water Numerous mucous glands keeps skin moist Can also secrete- foul taste/ poison Live in moist areas Tend to be active at night Can be affected by environment (indicators) Chapter 40 Amphibians

skeleton Strong internal skeleton Bear weight of body Strong limbs to support body Ability to jump and land Chapter 40 Amphibians

Circulatory system 2 separate loops Pulmonary circulation- carries deoxygenated blood from heart to lungs and back to heart Systemic circulation- carries oxygenated blood from the heart to the body and back to the heart 3 chambered heart Chapter 40 Amphibians

Chapter 40 Amphibians

Respiration Larval by gills and skin Adult – lungs (pulmonary respiration) and skin (cutaneous respiration) Positive pressure breathing- pumps air into the lungs Chapter 40 Amphibians

Digestive system Carnivorous Small insects, arthropods, mice, snakes, fish, amphibians, birds Larva- herbivores (algae, bacteria, plants) Pharynx  esophagous  stomach  liver  gallbladder  small intestine  large  cloaca Chapter 40 Amphibians

Excretory system Kidney (primary) filter nitrogen and waste Flushed out as urine Kidney  urinary ducts  cloaca  urinary bladder (water storage) can be reabsorbed during dry times Transform ammonia into urea Chapter 40 Amphibians

Nervous system Brain (same size as fish) Olfactory lobes (sense of smell) Long lobes of cerebrum (behavior learning) Optic lobes – process info from eyes Cerebellum- muscular coordination Medulla oblongata- organ functions, heart 10 pairs of cranial nerves Chapter 40 Amphibians

Sense organs Lateral lines (only in water) Nicitating membrane- covering of eyes Tympanic membrane- eardrum Columella- small bone that extends between the tympanic membrane and the inner ear Chapter 40 Amphibians

Objective 40.3 Explain how a male frog attracts a female of the same species Discuss the reproductive system in frogs Describe the changes that occur during metamorphosis in frogs Identify two examples of parental care in amphibians Chapter 40 Amphibians

Reproduction in amphibians One of the biggest differences between aquatic and terrestrial life-forms is their method of reproduction. Most amphibians depend on water for reproduction. They lay their eggs in water and spend the early part of their lives as aquatic larvae. Chapter 40 Amphibians

Courtship and fertilization Mating call- frogs croak Males have vocal sacs Female responds to same species External fertilization Eggs  tadpoles  hind legs appear  frog legs appear  young frog  adult Thyroxine – produced by thyroid gland to stimulate metamorphosis Chapter 40 Amphibians

Chapter 40 Amphibians

Parental care Parent care can increase chances of survival Male remain with eggs Rhinoderma darwinni- takes them in vocal sacs till hatch Gastric –brooding frogs in Australia- swallow eggs Eleutherodactylus- sit on eggs Chapter 40 Amphibians

Chapter 40 Amphibians

Chapter 40 Amphibians

Virtual Dissections http://www.mhhe.com/biosci/genbio/virtual_labs/BL_16/BL_16.html Chapter 40 Amphibians