2. FISH
All fish are aquatic vertebrates. Some live in fresh water and some in salt water.
 Body features
✓ FUSIFORM body.
✓ Fish limbs are FINS. Most fish have: 2 pectoral fins, 2 pelvic fins, one caudal fin, one anal fin and one or more dorsal fins. However, there are exceptions.
✓ Their body is covered with SCALES, which are overlapped. Sharks and rays have small denticles instead of flat scales.
✓ They have a sensory organ, the LATERAL LINE, which detects water vibrations.
✓ Most fish have a NATATORY BLADDER, an internal sac filled with air, which they use to control their depth.
✓ They always have a tail (with the caudal fin).
✓ They breathe through GILLS, so they cannot breathe outside the water. In typical fish, gills are protected by a bony piece called OPERCULUM. In sharks, rays, and other fish, there’s no operculum.
✓ Moste are carnivorous, but there are many herbivorous and omnivorous.
✓ They are generally OVIPAROUS, but some sharks are OVOVIVIPAROUS.

    Fish have a fusiform body, with fins and a tail
Natatory bladder
  Most fish have a bony operculum covering their gills, and they have overlapped scales. Sharks and rays don’t have an operculum and have small denticles instead of scales.
 The lateral line of fish is a sensory organ which can detect water vibrations.
   There are 2 major groups of fish:
(sharks and rays)
✓Marine animals only.
✓Their skeleton is made of cartilage
✓Their body is covered with small denticles
✓They don’t have an operculum.
(most fish, such as, hake, salmosn, carp…)
✓Marine and freshwater animals ✓Their skeleton is made of bone
✓Their body is covered with overlapping scales.
✓They have an operculum
Adults are terrestrial animals, although they need need to live in wet environments. However, juveniles are aquatic.
 Body features
✓ Amphibians have 4 LEGS. In frogs and toads, hind legs are adapted to jump.
✓ Their skin is very thin, smooth and has no covering. They need to keep it moist because they use it to breathe.
✓ Frogs and toads don’t have a tail. Salamanders and newts, do.
✓ They are POIKILOTHERMS. They are more
abundant in wet warm areas.
✓ Their life has two stages: the larva or TADPOLE and the ADULT, which are very different. The transition from one to the other takes place by means of a set of transformations, called METAMORPHOSIS.
✓ Adults are terrestrial animals, so they have LUNGS to breathe, although their moist skin is also useful to absorb oxygen from water. Tadpoles are aquatic and they have external gills.
✓ Adults are commonly carnivorous and tadpoles are herbivorous.
✓ Frogs and toads usually have external fertilization. Salamanders and newts have internal fertilization.
✓ Most are OVIPAROUS. Their eggs don’t have a hard shell, so they must be laid in water. Some salamanders are ovoviviparous.
 2 groups of amphibians
  Frogs and toads
Salamanders and newts

✓Without a tail ✓External fertilization ✓Oviparous
✓With a tail
✓Internal fertilization ✓Oviparous y ovoviviparous
It is a set of deep transformations that some animals undergo since they are born as a larva, until they become an adult.
✓No legs ✓Gills ✓Herbívorous
✓No tail
✓With legs
✓Carnivoruos (insects)
 Fish and amphibians – activities
PP16. Make a table to compare cartilaginous and bony fish.
PP17. Some ambphibians in tropical regions, such as caecilians (see picture), don’t have legs. Why are they considered to be amphibians and not reptiles, like snakes?
PP18. What are some adaptations of fish to aquatic life? PP19. Describe how respiration changes as amphibians grow.
PP20. What are the two orders of amphibians? Find out examples in the Iberian fauna.
PP21. Do some research on amphibians decline. What is the situation? What are the main causes?
Most reptiles are terrestrial animals, but some spend a lot of time in the water (ex. sea turtles).
Body features:
✓ They have 4 LEGS which are small and laterally projected, so they drag themselves along on their belly. Exceptions: snakes don’t have legs, and sea turtles have modified their legs into paddle- like flippers.
✓ They always have a tail.
✓ Their body is covered with hard SCALES, placed edge to edge without overlapping.
✓ Some reptiles need to renew or SHED their skin to grow. They lose their old skin and replace it by a new one.
✓ Turtles have a hard round bony shell called a CARAPACE.
✓ They are POIKILOTHERMS, so they can’t autoregulate their body temperature. That’s why they are rare in cold areas.
✓ They have LUNGS.
✓ They are usually carnivorous, although some are herbivorous (ex. Iguanas).
 ✓ They are heterosexual and INTERNAL FERTILIZATION.
✓ They are oviparous, but they don’t incubate their eggs. Some snakes are ovoviviparous.

   Reptiles have 4 legs and a tail. Sea turtles have paddle-like
flippers to instead of legs.
 Snakes and lizards shed their skin to grow. They lose the old one and produce a new one.
A reptile’s body is covered with scales placed edge to edge.

   Reptiles are oviparous animals. They don’t incubate their eggs.
 Most reptiles are carnivorous but iguanas are herbivorous.
All birds are terrestrial vertebrates. Most are adapted to fly, but some birds cannot fly even though they have wings (ex. Ostrich)
 Body features
✓ They have a neck, which is sometimes very long.
✓ The body shape is aerodynamic.
✓ 4 limbs: the 2 back limbs are legs, covered with scales and with four fingers; the 2 front limbs are wings.
✓ They have a horny mandible: the BEAK or BILL and no teeth..
✓ All birds have a tail.
✓ Their bones are hollow and light.
✓ Their breastbone is highly developed, so that strong ving muscles can attach to it. It’s called the KEEL.
✓ The body is covered with feathers (except for the legs and beak). Each feather has an axis or rachis, barbs which spread out on each side of it and a calamus, which joins the feather to the body.
✓ They have LUNGS connected to AIR SACS that take up most of their body and reach into their bones. This make them lighter and refrigerates their body more efficiently.
✓ Their feeding is diverse and it varies among species. The shape of the bill adapts to the diet.
✓ They are heterosexual and have internal fertilization.
✓ They are OVIPAROUS and incubate their eggs.

  Wings Tail
or bill
Trunk Legs
   A feather
Rachis Barbs
  Birds have LUNGS connected to AIR SACS that take up most of their body and reach into their bones. This make them lighter and refrigerates their body more efficiently.

 There are many types of birds…
Their beak is adapted to their feeding.
 Eagle Pelican
   Humming bird
Most mammals are terrestrial animals. Only bats can fly. There are some aquatic mammals too like whales and dolphins.
 Body features
✓ They have a neck and a tail. Some don’t have the tail (human beings and apes).
✓ They have many glands, specially mammary glands, which produce milk to feed the new-born.
✓ They have lips for suckling and teeth.
✓ 4 limbs, normally legs. Aquatic mammals have fins and bats have 2 wings and 2 legs.
✓ Their body is covered with fur.
✓ They have LUNGS. That means they cannot breathe underwater.
✓ They are VIVIPAROUS. Exception:
MONOTREMES are oviparous.
✓ All suckle when they are young. Afterwards, they have a very diverse feeding.

   Mammals have 4 limbs, normally legs. Aquatic mammals have fins and bats have 2 wings and 2 legs.
  All mammals suckle their young