The structure of mammalian skin Epidermis DermisSubcutaneous layer of fat
Function of the adipose/fat layer:1. provides a store of energy2. forms an insulating layer: prevents heat loss Subcutaneous layer of fat
Question: Sep, 2011Give a biological explanationfor each of the following:Aquatic mammals such aswhales have a thick layer ofblubber. (3)
3 layers in epidermis: cornified granular malpighian
New skin cells are made all the time at the : cornified granular malpighian
Growth of the epidermis: cornified4 The dead cells become hard and flat and flake off. The cells are cut3 off from the blood granular supply and so die. 2 This cell enters the granular layer. Cells in this layer malpighian1 divide to produce two cells.
Functions of the cornified layer:i) reduces water lossii) keeps out microbes Cornified layer dead cells
Function of the malpighian layer: cells divide by mitosis to form the granular layer Granular layer Malpighian layer: produces melanin
Functions of melanin:1. absorbs ultraviolet rays2. gives colour to the skin
What is present in the dermis? sensory nerve endings sweat glands hair follicles capillaries Let’s f ind outthe f unction of each.
Receptors serve as receivers for the body, keeping it informed of changes in its environment.
What is present in the dermis? sensory nerve endings sweat glands hair follicles capillaries
sweat pore evaporationSectionthrough skin epidermis The sweat gland dermis extracts sweat from the blood and passes it up sweat duct the duct to the skin surface where it evaporates sweat gland blood vessel 0.25 mm
Question: SEP, 2010What is sweat made up of? (3) Water Salts Urea A little lactic acid
Sweat cools the body as it evaporates The skin
VasodilationIf thetemperaturerises, the bloodvessel dilates(gets bigger). This means more heat is lost from the surface of the skin
VasoconstrictionIf thetemperaturefalls, the bloodvessel constricts(gets shut off). This means less heat is lost from the surface of the skin
Give a reason for this observation. A child looks pale in the face on a cold day but red after running a race.Vasoconstriction to Vasodilation to reduce heat loss. increase heat loss.
Spot 3 ways shown in the diagramthat help cool the body on a hot day. Cold 1 Hot 2 3
5 functions of the skin:1. Protection – barrier to microbes reduces water loss absorbs UV rays
5 functions of the skin:2. Sensationsensory cells make the bodyaware of the changes around itthrough pain, touch, heat coldand pressure
5 functions of the skin:3. Formation of vitamin Dby the action of sunlight on the skin
5 functions of the skin:4. Temperature regulationhelps to keep a constant body temperature5. Excretionremoves urea in sweat
Question: Sep, 2011Give a biological explanation for each of thefollowing: African elephants flap their large ears frequently in hot weather. (4)
Balance in heat gain and heat loss HEAT GAIN HEAT LOSS
Ways to GAIN heat1) INTERNAL CHANGES2) EXTERNAL CHANGES
Ways to GAIN heat 1) INTERNAL CHANGES i) reactions release heat ii) muscular contractions release heat IRATIONRESP
Ways to GAIN heat2) EXTERNAL CHANGESi)body absorbs heat if temperature is more than 37°Cii) hot foods and drinks add heat
Ways to LOSE heata)conduction, convection, radiationb) evaporation of sweatc) cold air inhaledd) cold drinks and food
Find the SA:Vol of the cubeArea of 1 side = length x width = 1 x 1 = 1 cm2Area of 6 sides = 1 x 6 = 6 cm2Volume = length x width x height= 1 x 1 x 1 = 1 cm3 Surface area to volume ratio = 6:1
Find the SA:Vol of the cubeArea of 1 side = 2 x 2 = 4 cm2Area of 6 sides = 4 x 6 = 24 cm2Volume = 2 x 2 x 2 = 8 cm3 Surface area to volume ratio = 3:1
What happens to the SA:Vol ratio as the cube increases?
2 cubes were immersed in a dye for the same amount of time. They were removed and cut in half. Explain the result.
Rate of diffusion is the same in all cubes BUT distance to centre is different
A LARGE organism has a small surface area to volume ratio which means:1. little heat is lost2. cannot take in oxygen from the body surface by diffusion
Curling up when cold reduces surface area for heat loss
A large organism needs a: Circulatory system Breathing system Why does an amoeba lack a circulatory system?Being small, it has a large surface area tovolume ratio. Materials reach all parts ofthe cell quickly.
A SMALL organism has a large surface area to volume ratio which means:1. a lot of heat is lost2. can take in oxygen from the body surface by diffusion
Arctic animals Are large Have small ears Thick fur
Two species of Lepus adapted to live at different temperatures. Explain how.
A baby and an adult, both naked,are placed in a room at a lowtemperature. Which one loses heatfaster and dies first? Why?Small body- Large body-large SA: Vol ratio small SA: Vol ratio
Rule is: LARGE animals in cold climates SMALL animals in hot climatesLarge body- Small body- little heat loss large heat losses
fish, reptiles, amphibians and invertebrates absorb heat from their surroundings - this is called basking are poikilotherms Marine iguana basking
birds and mammals produce heat inside their bodies are homeotherms
Endotherms insulate their body by: Feathers FurBlubber
Question: MAY, 2011Give a biological explanation for each of the followingsituations:a)A volunteer student sat in a sauna (a chamber witha temperature reaching 80°C for an hour. Sweatproduction increased rapidly. (3)
Increase in external environmentaltemperature will result in an increase in theinternal body temperature.Body produces sweat to regulate the internaltemperature.Evaporation of sweat cools down the bodytemperature.
Question: MAY, 2011Give a biological explanation for each of the followingsituations:b) A young child falls in a frozen lake in winter. Thechild starts shivering vigorously after being pulled outof the lake. (4)
Muscles contract and relax quickly – thisproduces heat.The heat generated in the muscles warms theblood as it flows through them.The blood distributes this heat all over thebody.
Question: MAY, 2011List THREE ways by which the parents of a childwho fell in a frozen lake in winter can preventfurther heat loss. (3)
Provision of dry clothes/moving child next to a warm environment such as a heater/removing cold clothes and covering child with a blanket/ Help child to take a warm bath Provide a warm drink or fluid such as soup.
Question: SEP, 2010Give a biological explanation for each of thefollowing statements:In cold weather we tend to shiver and eatmore. (3)Shiver: to produce heatEat more: higher rate of respiration = moreheat