Key Concepts in Biology and Ecology
Adaptations
Features which enable organisms to survive are called adaptations. Adaptations can be classified as anatomical, physiological, or behavioural.
Types of Adaptations
- Anatomical adaptations are the structures of an organism that are modified to perform an adapted function.
- Physiological adaptations are features of the processes inside an organism’s body that increase its chance of survival or reproduction.
- Behavioural adaptations are any actions by organisms which help them to survive or reproduce.
Camel Adaptations
Camels are large animals (Figure 5.15 – not included) which live and breed in the desert, which is the hottest, driest, and most challenging environment. Incredible adaptations allow the camel to survive and thrive as a herbivore there.
Anatomical Adaptations of Camels
- Presence of closable nostrils and long eyelashes, which help keep out wind-blown sand.
- Having large and flat feet with tough pads allows the weight of the camel to be spread out as it walks over sand and also prevents heat damage.
- Tough pads on the knees prevent damage from hot sand when the camel rests.
Physiological Adaptations of Camels
- A camel can withstand a wide variation of internal body temperature and can allow its body temperature to vary over 6°C.
- The fatty tissue in the hump acts as a food store. As the fat is broken down to release energy during cellular respiration, water is produced as a by-product. This water helps camels survive without drinking water for a long period.
- The kidneys minimize the production of urine.
The Sulphur Cycle
The sulphur cycle describes the movement of sulphur through the atmosphere, mineral forms, and through living things. Sulphur is an essential component of living organisms. It is a constituent part of many proteins and enzyme cofactors.
The majority of the Earth’s sulphur is stored underground in rocks and minerals. When the rocks are weathered, the stored sulphur is released. Once sulphur is exposed to the air, it combines with oxygen and becomes sulphate (SO₄²⁻). Plants and microbes assimilate sulphate and convert it into organic forms.
As animals consume plants, the sulphur is moved through the food chain and released when organisms die and decompose.
Sulphur within the soil can also be mineralized into inorganic forms and incorporated with metals (e.g., iron sulphide) and fossil fuels (e.g., coal). When fossil fuels are burnt or during volcanic eruptions, sulphur is released into the atmosphere as sulphur dioxide (SO₂) and hydrogen sulphide (H₂S). Sulphur eventually settles back into the Earth or comes down within rainfall since sulphur is dissolved in the form of weak sulphuric acid (H₂SO₄).
The sulphur cycle outlines how different forms of sulphur are cycled within the environment.
Sex Determination
In man, and apparently in all other mammals, the presence of the Y chromosome may determine a tendency to maleness. Normal males are chromosomally XY and females are XX. This produces a 1:1 sex ratio in each generation. Since the male produces two kinds of gametes as far as the sex chromosomes are concerned, he is said to be the heterogametic sex. This mode of sex determination is commonly referred to as the XY method.
Kidney Structure
Each kidney consists of two regions: the outer region, the cortex, and the inner region, the medulla, which has bulges called ‘pyramids’ pointing towards the concave side of the kidney. The pyramids lead to a funnel-like structure called the pelvis. The pelvis connects with the ureter, carrying the urine to the bladder (Figure 4.14 a and b – not included).
There are about one million nephrons in each kidney. Nephrons are the basic functional unit of the kidney and each consists of a glomerulus, a Bowman’s capsule, and a long renal tubule.
- A glomerulus is a cluster of capillaries located inside a cup-like structure called Bowman’s capsule.
- A renal tubule comprises three portions: the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule.
The tubules of all the nephrons join with the collecting duct.
Ecological Pyramids
Ecological pyramids are diagrams that represent the relative amounts of organisms at each trophic level in a food chain. There are three main types:
- Pyramids of numbers, which represent the numbers of organisms in each trophic level in a food chain, irrespective of their mass.
- Pyramids of biomass, which show the total mass of the organisms in each trophic level, irrespective of their numbers.
- Pyramids of energy flow, which show the flow of energy at each trophic level in an ecosystem.
The base of the energy pyramid indicates the energy available within primary producers. The second and third trophic levels consist of primary consumers and secondary consumers, respectively.
Consider the two food chains:
- grass → grasshoppers → frogs → carnivorous birds
- oak tree → aphids → ladybird beetles → insectivorous birds
Abiotic Factors
Abiotic factors are non-living physical or chemical factors. They include climate, such as light intensity and duration, temperature, and other weather conditions, and water availability. Soil conditions also include clay content, nitrate level, particle size, water content, and pH. Other abiotic factors are specific to a particular habitat, such as salinity (salt content) in an estuary, flow rate in a river, or oxygen concentration in a lake or pond, and pollution. The factors that will affect population sizes and distribution of organisms will depend on the type of ecosystem.
For example, in a river, some of the main abiotic factors could be depth of water, type of materials at the bottom of the river (stones, sand, mud, etc.), concentration of minerals in the water, pH level of the water, oxygen concentration, and turbidity of the water.
Lithosphere
Lithosphere means the mantle of rocks constituting the Earth’s crust. The Earth is a cold spherical solid planet of the solar system, which spins on its axis and revolves around the sun at a certain constant distance. The Lithosphere mainly contains soil, Earth rocks, mountains, etc., and is divided into three layers: crust, mantle, and core (outer and inner).
Biosphere
The Biosphere, also known as the life layer, refers to all organisms on the Earth’s surface and their interactions with water and air. It consists of plants, animals, and microorganisms, ranging from the tiniest microscopic organisms to the largest whales in the sea.
Blood Sugar Regulation
Glucagon acts on the cells in the liver and causes them to convert some of their stored glycogen into glucose and so restore the blood sugar level. Insulin has the opposite effect to glucagon. If the concentration of blood sugar increases (e.g., after a meal rich in carbohydrate), insulin is released from beta cells of the Islets of Langerhans. When the insulin reaches the liver, it stimulates the liver cells to take up glucose from the blood and store it as glycogen. Thus, the concentration of blood glucose is restored at a normal level.
Insulin has many other effects: it increases the uptake of glucose in all cells for use in respiration, promotes the conversion of carbohydrates to fats, and slows down the conversion of protein to carbohydrates.