FISHESFISHESChapter 30Chapter 30

Learning Targets 30.2Learning Targets 30.2

Identify the characteristics of fishes

Summarize the evolution of fishes.

Explain how fishes are adapted for life in water.

Describe the three main groups of fishes

Identify the characteristics of fishes

Summarize the evolution of fishes.

Explain how fishes are adapted for life in water.

Describe the three main groups of fishes

Fishes

Fishes are aquatic vertebrates that are characterized by

Paired finsScalesGills

Fishes are so varied, however, that for almost every general characteristic there are exceptions.

Example: Catfish don’t have scales

Evolution of Fishes

They did not arise directly from tunicates or lancelets.

Fishes and non-vertebrate chordates evolved from common invertebrate ancestors.

The evolution of jaws and the evolution of paired fins were important developments during the rise of fishes

Evolution of Fishes The first fishes were thought to be

jawless creatures whose bodies were armored with bony plates

The Arrival of Jaws and Paired FinsJaws make it possible for vertebrate to nibble

on plants and to munch on other animalsAnimals with jaws are able to eat a wide

variety of foodThey are able to defend themselves by bitingThese adaptations alone have increased

survival

Form and Function in Fishes

Adaptations to aquatic life include:Various modes of feedingSpecialized structures for gas exchangePaired fins for locomotion

Feeding and Respiration in Fishes

Feeding:Every mode of feeding is displayed

Respiration:Most fishes exchange gases using gills

that are located on either side of the pharynx

Circulation in Fishes

Fishes have a closed circulatory system

The system has:HeartIt pumps blood around the body in a single loop

Single Loop Circulatory SystemSingle loop from the heart to the gillsFrom the gills to the rest of the bodyThen back to the heart

Excretion

Like many other aquatic animals, most fishes get rid of nitrogenous waste in the form of ammonia.

Some of the waste will diffuse through the gills into the surrounding water

Others will remove waste by kidneysThese are excretory organs that filter wastes

from the blood.

Excretion cont.

Kidneys help to control the amount of water that is in their bodies

Fishes in saltwater tend to lose water by osmosis and excrete concentrated wastes

In contrast, freshwater fishes pump out plenty of dilute urine.

Response

Fishes have well developed nervous systems organized around a brain with many parts

The cerebrum is responsible for all voluntary activities in the body

The cerebrum of fish primarily processes the sense of smell

Fish Brain

Fish Brain

Response The optic lobe processes information

from the eyesThe cerebellum coordinates body

movementsThe medulla oblongata controls the

functioning of many internal organsIn addition, fishes use a lateral line

system to sense motion of other fishes or prey

Fish Brain

Fish Brain

Movement

Fishes move by alternately contradicting paired sets of muscles on either side of their backbone.

Many bony fishes have an internal, gas filled organ called a swim bladder

It adjusts the fishes buoyancy

Reproduction

The eggs of fishes are fertilized either internally or externally

Types of Development:OviparousOvoviviparousViviparous

Reproduction Oviparous:

Eggs hatch outside the mother’s bodyExample: Salmon, fish, and crocodiles

Ovoviviparous:Eggs stay in the mother’s body and the young are then

born aliveObtain the nutrients needed from the egg yolkExample: Insects, fish, snakes, and lizards

Viviparous:The young are born aliveThe young obtain nutrients directly from the mother’s bodyExample: Humans, snakes

Groups of Fishes

Groups of Fishes

Groups of Fishes

When you consider their basic internal structure, all living fishes can be classified into three groups:

Jawless FishesCartilaginous FishesBony Fishes

Jawless Fishes

Have no teeth or jawsSkeleton are made of fibers and

cartilageThey lack vertebrae and keep their

notochords as adultsModern jawless fishes are divided into

two groups:LampreysHagfishes

LampreyLamprey

HagfishHagfish

Sharks and their Relatives

The class: ChondrichthyesContain:

Sharks, Rays, Skates, Sawfishes and Chimaeras

The skeletons of these fishes are built entirely of cartilage….NOT bone

Bony Fishes

The class: OsteichthyesContain: Combtooth Blenny, Emperor

Angelfish, Flying Fish, Peacock Flounder, Leafy Sea Dragon

Examples: Almost all living bony fishes belong to a huge group called ray-finned fishes

The skeletons of these fishes are made of hard, calcified tissue called bone

The End!The End!

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