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Meet the Fish
So what exactly is a fish? You probably think the answer is obvious. You may say that a fish is an animal that swims in the ocean or a lake. But there is lots more to fish than that. Fish are aquatic vertebrates, which through evolution became a dominant form of sea life and eventually branched to create land vertebrates. They have a number of characteristic traits and are classified into two major groups: jawless and jawed fish. Jawed fish are further divided into those with bones and those with just cartilage. Fish, in general, are important in many ways to humans - economically, recreationally and culturally. Perhaps you can think of some of these ways?
Fish are vertebrates that are typically ectothermic, are covered with scales, have jaws and have two sets of paired fins and several unpaired fins. A typical fish has a streamlined body that allows it to swim rapidly, extracts oxygen from the water using gills or an accessory breathing organ to enable it to breathe atmospheric oxygen, and lays eggs that are fertilized internally or externally. Fish range in size from the 16 m (51 ft) whale shark to the 8 mm (just over 1⁄4 of an inch) stout infantfish.
Traits of a typical fish include:
• Vertebrate
• Ectothermic
• Scales, Jaws
• Two sets of paired fins
• Several unpaired fins
• Streamlined body
• Gills or an accessory breathing organ
• Lays eggs that are fertilized internally or externally
Instructions - complete the following
Lessons
Notes - see Notes for Chp 30, 31, 32
Watch the following
Animation - Fish Respiration
Animation - Virtual Salmon Dissection
Animation - Phylogenetic Tree of the Chordates
Animation - Vertebrate Evolution
Videos
Coelocanth - as Fish move to Land
Mudskippers - Fish on Land
Miller & Levine pg 771-781
Amphibians
Amphibians are ectothermic vertebrates, belonging to the class Amphibia and consist of three orders: Caudata, containing the salamanders and newts; Anura, consisting of frogs and toads; and Apoda, containing the caecilians. The larvae are typically aquatic and breathe using gills. The adults are typically semi-terrestrial and breathe both through moist skin and by lungs.
For the purposes of reproduction, most amphibians are bound to fresh water. Although there are no true seawater amphibians, a few tolerate brackish (slightly salty) water. Some species do not need any water whatsoever, and several species have also adapted to arid and semi-arid environments, but most still need water to lay their eggs.
In general, the life cycle of amphibians begins with a shell-less egg stage, usually laid the previous winter in a pond. A larval stage follows in which the organism is legless, fully aquatic and breathes with exterior gills. After hatching, the larvae start to transform gradually (metamorphosis) into the adult’s appearance, including loss of gills, growth of four legs, and the ability to live in a terrestrial environment.
Adaptations for living in a terrestrial environment include replacement of gills with another respiratory organ, such as lungs; a development of glandular (containing cells, a group of cells, or an organ producing a secretion) skin to avoid dehydration, and the development of eyelids and adaptation to vision outside the water. An eardrum also develops that separates the external ear from the middle ear and, in frogs and toads, the tail disappears.
Instructions - complete the following
Lesson
Notes - see Notes for Chp 30, 31, 32
Watch the following
Animation - Three-Chambered Frog Heart
Animation - Respiratory Organs in Amphibians
Soundbytes - frog songs
The Caecilians - snake-like amphibians
Miller & Levine pg 782-789
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