The Perch

Question 1

Classification

Answer 1

• perch are vertebrate animals (they have backbones)

* most bony fish have a swim bladder used to maintain buoyancy or as a lung

Question 2

Digestion

Answer 2

• perch eat smaller fish, aquatic insects, crayfish and snails
• they feed by creating a partial vacuum in their mouths and sucking in prey
• they have pyloric ceca at the junction of the stomach and intestine to increase the surface area for absorption

Question 3

Gas exchange

Answer 3

• perch get their oxygen from water
• it would take too much energy to inhale and exhale water into lungs, therefore fish have gills
• gill filaments are made of small thin walled lamellae
• water is gulped into the mouth while the gill covers are closed, then the mouth closes, forcing water through the gills
• deoxygenated blood flows through the gills from back to front, the counter-current system maximizes gas exchange

Question 4

Circulation

Answer 4

• perch have a closed circulatory system
• their hearts have only one pump
• a single atrium collects blood and a single ventricle pumps it back out

Question 5

Reproduction

Answer 5

• sexes are separate in perch
• females lay eggs on the bottom and males release sperm over the eggs
• the eggs hatch in 2 or 3 weeks, depending on the temperature
• perch don’t care for their young

Question 6

Excretion

Answer 6

• nitrogen wastes diffuse into the water through the gills
• perch skin is waterproof but the mouth and gills freely allow water to diffuse into the blood
• the perch kidney produces large volumes of dilute urine, to eliminate all this extra water