BIOGEOSPHERE
Bilingual Biology and Geology
I.E.S. "J.S.Elcano (Sanlúcar Bda.)
6. Fish
This is the most numerous group of Vertebrates.
It is estimated that there are more than 25,000 species of fish.
Fossil evidence indicates that fish appeared about 500 million years ago.
a) Habitat
All fish are aquatic vertebrates.
We can find them in fresh water, living in lakes or rivers, but the most part of them are marines.
b) Morphological characteristics
- Their body is spindle-shape (fusiform) to make them easier to move into
water. It is divided into: head, trunk and tail.
- Their limbs are fins.
- Their skin is covered with scales, which protect the body and reduce
the friction with water
- Most of them have swim bladder.
It is a balloon-like organ filled with gases which help them to float.
c) Vital functions:
Nutrition:
The digestive system is complete.
They have a mouth with teeth,
a stomach, an intestine and an anus.
It opens outside by the cloaca.
Their type of feeding is very diverse.
They breathe through gills.
Fishes have simple circulation.
This means that blood follows
a single circuit: heart-gills-body-heart.
The fish heart has only two chambers:
an upper atrium and a lower ventricle.
Only blood without oxygen flows through it.
They have two primitive kidneys.
Interaction
They have a well developed brain and sense organs: eyes (without eyelids), ears (without auricles), taste, smell and touch. In addition they have an exclusive sense organ, the lateral line. It is row of sensorial receptors along each side of the body and the head. This system detects water vibrations.
They are poikilotherms (cold-blooded).
Reproduction:
Most of them have external fertilization. The female lays eggs in the water and the male drops sperm on them.
They are oviparous and usually do not care the eggs or young.
d) Classification:
- Bony fish
They are the most numerous group of fish (95 %).
Their skeleton is made of bone.
The skin is covered by scales.
They have protected the gill openings by an operculum.
They have a very diverse feeding kind.
- Cartilaginous fish
Their skeleton is made of cartilage (no bone)
The skin is covered by dermal denticules (no scales). It is similar to sandpaper.
They do not have protected the gill openings by an operculum.
They do not have swim bladder.
They are mainly predators.
READING ACTIVITIES
After reading the text, copy and answer the following questions into your notebook:
Remember: you must make complete sentences.
6.1. Answer the following questions:
a. Which organ allows fish to breathe into water?
b. What is the swim bladder?
c. Which morphologic characteristics allow fish to move into water?
6.2. Complete the comparative chart about cartilaginous fish and bony fish.
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Bony Fish |
Cartilaginous Fish |
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Operculum |
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Skeleton made of… |
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Skin covered by… |
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Swim bladder |
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Examples |
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Now listen and indicate what type of fish describes each stament.
6.3. Listen and identify which characteristic of fish is described:
a. Spindle-shape body (fusiform)
b. Scales
c. Fins
d. Gills
e. Swim bladder
f. Lateral line
Now,
check
your
answers!
LISTENING ACTIVITIES
Download this worksheet
and complete it,
while you listen this audio.
SPEAKING ACTIVITIES
Now, in turns with your partner,
answer the questions in the worksheet.
(Diccionario Ing-Esp)
(Juegos de vocabulario)
(Visual dictionary)
(Visual dictionary)
(Glosario de C. Naturales)
(Science audio-glossary)
(Science audio-glossary)
(Pronunciación)
(Enciclopedia de C. Naturales)
(Tabla periódica)
Eva Mª
López Rodríguez
Departamento
Biología y Geología
IES " J. S. Elcano"
Sanlúcar de Barrameda