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Fish Head Dissection Lesson

Fish Head Dissection Lesson

Welcome to our Fish Head Dissection Lesson aimed at GCSE students.

We have a fish head dissection video demonstrating the methodology of the classroom dissection of a fish head.  We have included a lesson plan and risk assessments that can be downloaded or simply reviewed here.

We hope to guide pupils through discovering as much as they can from the fish heads!

Aim: To explain how the structure of the gill in fish is related to its function.

GCSE Biology

Methodology:

  • Rinse the fish head thoroughly under cold, running water and place in dissection tray.
  • Open the mouth and note the teeth (depending on species).
  • The lower jaw moves up and down to take in water.
  • Use forceps to move the operculum in and out, showing how it moves during ventilation. The operculum should be stiff to move, lift the operculum and identify the gill filaments and the gill slits, which are the spaces between the gills.
  • Push onto the bottom of the mouth to see the floor of the cavity.
  • Gently push a glass rod into the mouth, through the buccal cavity and through a gill slit to show the pathway of water during ventilation.
  • Use scissors to cut the operculum off where it is attached to the head. NB it is a hard structure.
  • Underneath are the (four) gills, supported by a bony gill arch.
  • Cut through the first gill arch, again it is quite strong so take care.
  • Submerge the fish gills in cold water. The gills should ‘fluff up’ – notice the large surface area.

 

  • Extra:  With fine scissors, cut off a few mm from a gill filament and place on a microscope slide. Place 2 drops of water on the material and cover it with a cover slip. Examine it under the microscope using a x4 and then a x10 objective lens.

 

Teaching Notes:

The Gills are used for gas exchange. They extract the dissolved oxygen in water and exchange carbon dioxide. They are made of thin filaments of tissue branches that are organized into folded structures that allow the surface area of gills to be large. This is important because there is less oxygen in water than in air and fish need to be able to take in enough oxygen so that they don’t suffocate. Fish breathe by taking in water through the mouth. Each gulp of water then flows into a gill chamber on each side of the head and over the gills. A hard bony covering, known as the operculum, protects the gills.

 

Observations to point out:

Locate the gills. These are protected by a covering known as the operculum.

Separate the gills using tweezers. How many gills are there? Most have four on each side of their head.

Use tweezers to examine the direction in which water flows over the gills, or squirt water through the mouth.

Note the gill rakers attached to the gill arch. They filter solids, preventing damage to the gill filaments.

  • Samples for Schools Fish Head
  • Dissection tray
  • Scalpel
  • Scissors
  • Mounting needle
  • Ruler or calipers with mm divisions
  • Paper towel

AQA: Topic 4.1.3.1

Students should be able to explain how the small intestine and lungs in mammals, gills in fish, and the roots and leaves in plants, are adapted for exchanging materials.

Edexcel: Topic 8.2

Explain the need for exchange surfaces and a transport system in multicellular organisms including the calculation of surface area: volume ratio.

Eduqas: Topic 2.1

Explain the need for exchange surfaces and a transport system in multicellular organisms in terms of surface area: volume ratio.

OCR 21st Century: Topic B5.1 (7)

Explain the need for exchange surfaces and a transport system in multicellular organisms in terms of surface area: volume ratio.

OCR Gateway: Topic B2.2a and B2.2b

Explain the need for exchange surfaces and a transport system in terms of surface area: volume ratio.

Describe some of the substances transported into and out of a range of organisms.