Evolution and Adaptation in Science
History of Science
As an example of the changes in ideas of this time, we will examine the behavior of a simple pendulum. Until the 16th century, Aristotle’s theory of pendulums held that the period (the length of time for one swing back and forth), depended on the amplitude (the distance the pendulum swung). We shall now test this idea, just as Galileo did.
A pendulum is a weight hanging from a fixed point by a string or wire which, when pulled back and released, is free to swing in and down due to gravity and then out and up because of its momentum, following a perfect arc.
Galileo found that the period was shorter for shorter pendulums but did not change with the mass or amplitude. Do your results agree?
Note that in each experiment above, only one thing has been changed in each experiment comparing the two pendulums. This is a common idea in science. In other words, we ensure everything stays the same between two situations, except for the one thing we want to study.
British biologist Charles Darwin was born in 1809, and in 1859 published one of the most scientifically important books ever written, On the Origin of Species by Means of Natural Selection. His work gave rise to the Theory of Evolution.
Each species had a distinct size, and beak shape, specifically adapted to the food the birds ate. Some ate seeds, other insects, and this reflected the food available on the individual islands the birds lived on. Darwin speculated that somehow the birds had changed to adapt to the environment they had found themselves in. This meant that slightly different environments had led to slightly different birds.
Natural selection is the process whereby the random mutations that naturally occur when a species reproduces lead to some individuals that are better at surviving in the environment than others. After many generations of such selective breeding, the species will have changed, or evolved, into a new species more capable of surviving in its environment.
Darwin simply realised that this can happen naturally to species in the wild, without artificial involvement. After a long period of such specialisation, this one species will have evolved into several different species, each one uniquely adapted to surviving in their own particular ecological niche. In this way, Evolution is the engine driving the great diversity of life we find on Earth.
Darwin’s book, The Origin of Species, was published in 1859.
Darwin’s theory has since been greatly expanded, especially with the work of modern genetics and DNA research making his work one of the most important contributions to science.
Language of Science
The current International System of Units used in science is known as SI for short. This consists of seven base units, from which all other units can be derived.
The Kelvin measure represents an absolute measure of temperature. Zero on the Kelvin scale is the temperature at which all thermal motion of the atoms and molecules in a substance stops. In other words, it contains no heat at all. For this reason, 0 K is known as absolute zero.
It is not possible to achieve a temperature colder than this. This is an incredibly cold temperature. Zero Kelvin is equivalent to -273.15ºC, which is why this scale is not in everyday usage. The Kelvin measure is very useful in science however, particularly in the study of Chemical thermodynamics and Physics where heat energy is part of the system being studied.
Compound SI units are combinations of the Base units shown above. We could have said that a speed of 50 m/s is 50 ‘zips’ but no one ever made up a new name for this quantity so we simply refer to the units which were used to calculate them.
Many compound units in common use have been renamed, often to honor a famous scientist who studied the quantity the unit measures. These are called derived units.
Scientific Notation
Biology
Genetics
Sex-linked characteristics are carried on the X or Y chromosomes. Some genetically-transmitted disorders such as hemophilia are sex-linked. The gene involved in blood-clotting is found on the X chromosome. As females have two X chromosomes, one from their mother and one from their father, usually only one of these might contain the hemophiliac gene. The other gene (on their other X chromosome) is normal and can compensate for the hemophiliac gene, so although they have the faulty gene, and can pass it on to their children, they do not themselves get the disorder. These females are called carriers. Males, however, only have one X chromosome, and if the X chromosome they inherit from their mother contains the hemophiliac gene, they have no protection against it and so they will suffer from hemophilia.
Out of these 4 possible combinations in their children, one will be a female carrier and one will be an affected male.
Evolution
Adaptations are features or behaviours that enable an organism to suit or fit its environment to increase its chances of survival.
The Process of Adaptation
If an organism becomes too specialised, it is very vulnerable if sudden change occurs. Each species must be able to adapt to a changing environment or it will become extinct. If an individual possesses a characteristic that gives it an advantage in the environment, any offspring that inherit this characteristic may have a better chance of surviving than those who do not have it.
Adaptations are either learned or are a result of accidental changes in the genetic material an organism receives from the previous generation. Changes in behaviour can be learned but no organism can just decide to change its physical structure and then make it happen. Most often, the physical changes that occur are negative and result in the death of an individual before it is able to reproduce. For example, many serious physical deformities are negative mutations which work strongly against the survival of an individual organism.
Some changes are neutral and neither help nor hinder the individual. For example, hair colour in humans is not a serious enough mutation to determine the life or death of an individual so variations in hair colour are passed along from generation to generation attached to genes which carry more important survival characteristics.
Those changes that are positive make an individual better able to survive and reproduce, thereby passing on the change to future generations. However, it will take several generations for a positive change to become widespread in a population but, when it does, it is known as an adaptation.
1.Physiological Adaptation is a change in the body’s chemistry that occurs in extreme conditions.
2.Structural Adaptation is an inherited physical feature that increases an organism’s chance of survival.
3.Behavioural Adaptations are inherited or learned behaviours that increase an organism’s chances of survival.(hibernation, migration, social structure, and learning)
Chemistry
Atoms are made up of even smaller subatomic particles (electrons, protons and neutrons).
An atom has two different regions:
Nucleus: very small and extremely dense. It has protons (positive charge) and neutrons (neutral/ no charge).
Shells /orbitals: surrounding the nucleus. They contain electrons (negative charge).
Elements:
The chemistry of an atom is determined by the number and arrangement of the electrons, so each kind of atom has different chemical properties.
Atomic Number (symbol Z): it is the number of protons in the nucleus of an atom of that element.
Mass Number (symbol A): the number of protons plus the number of neutrons in the nucleus.
Isotope Symbol: the combination of atomic and mass number of an element. The mass number is always written to the upper left of the element symbol and the atomic number is always written to the lower left: A X (Element Symbol) Z
From the isotope symbol we can determine the number of protons and electrons in the atom (atomic number) and the number of neutrons: mass number –atomic number= number of neutrons
Ions
The nucleus of an atom cannot be easily changed, except for the radioactive elements.
It is extremely difficult to break up the nucleus of a normal atom but it is relatively easy to change its number of electrons.
Ions are atoms that have either lost or gained electrons. These are only lost or gained from the outer shell.
In ions, the number of positive and negative charges are not equal. The ion has an overall charge, either positive or negative.
A negative ion is produced when an atom gains one or more electrons.
Positive Ions:
A POSITIVE ION IS PRODUCED WHEN AN ATOM LOSES ONE OR MORE ELECTRONS. A positive ion is called cation and a negative ion is called an anion.
Physics
A) Newton’s First Law states
‘An object remains at rest or travels with a constant speed in a straight line unless acted upon by an external unbalanced force.’
This means that once an object is moving, it will keep moving unless an external force acts on it. An example of this would be a ball rolling along a flat road; it would keep moving forever but it eventually stops because of the friction between it and the road, which causes the ball to lose energy.
In physics however, we are interested not only in the distance and speed but also in the direction the object is traveling. We therefore talk about the displacement and velocity of a moving object. The displacement is how far the object has moved from its starting point in a specific direction. The diagram below illustrates this idea.
ABC
WestEast
A car is at point B. It drives west to point A then it turns around and drives east to point C.
The distance covered by the car is BA + AC but this does not take direction into account.
The displacement, however, is how far the car has moved from its original position in a specific direction. In traveling from A to C it had to return to B, its starting point, so the displacement is only BC. From the point of view of B, the direction BA (west) would be seen as a positive direction, and then the direction AC (east) would be seen as the opposite or a negative direction.
If BA is 2 km and AC is – 6 km, the overall displacement would be BA + AC = +2 +(– 6) = – 4 km
= 4 km East
Speed is measured as distance traveled per unit of time (e.g. 80 km/h) which is expressed mathematically by the formula:
speed = distance / timeorv = d/t
However velocity = displacement / time or ????⃗ = ????⃗⁄????
where ????⃗ = velocity, ????⃗ = displacement and t = time
Velocity and displacement are called vector quantities because they contain information about direction.
Newton’s Second Law explains how force affects an object. It states:
‘When an unbalanced force is applied, the velocity of the body is changed. In other words, an unbalanced force causes an acceleration.’(Moyle et al 1986, p142)
In other words, when a force is applied to an object, its speed increases by a fixed amount each second the force is applied.
Newton’s Second Law can be expressed mathematically as F = ma
where F = the force applied, m = the mass, and a = the acceleration.
Gravity: force attracting two objects with mass. The Earth, being an object with a large mass, holds objects on its surface (rocks, balls, us, etc.) to it by a force of gravity.
Mass is the amount of matter that constitutes an object.
Weight is the force due to gravity that is directly proportional to the mass of the object.
Newton’s Third Law is about actions and reactions. It states:
‘Whenever an object exerts a force on another object (action force), there is an equal force in the opposite direction from the second object onto the first (reaction force) for the same length of time.’
Earth Science
Earth Science is the study of the Earth and its processes.
The lithosphere is the rocky portion of the Earth’s surface between 100 and 200 km thick.
The atmosphere is the gaseous envelope surrounding the planet.
The hydrosphere is the part of the Earth composed of water including clouds, atmospheric water vapour, oceans, ice caps, glaciers, lakes and rivers.
The Earth has very distinct layers or zones:
1.The inner core is at the centre,and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C. With its immense heat energy, the inner core is like the engine room of the Earth.
2.The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel. It is still extremely hot, with temperatures similar to the inner core.
3.The mantle is the thickest layer. It has a thickness of approximately 2,900 km. The mantle is made up of semi- molten rock called magma. In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt.
4.The crust is the outer layer of the earth. It is a thin layer only up to 60 km thick. The crust is the solid rock layer upon which we live.
Volcanology is the study of volcanoes and their eruptions.
If a volcano is still likely to erupt today, it is classified as active. If it has not erupted for considerable length of time but it can still become active, it is classified as dormant. If it has not erupted during any period in recorded history, it is classified as extinct.
The Ring of Fire is a major area in the basin of the Pacific Ocean where many earthquakes and volcanic eruptions occur. In a large 40,000 km (25,000 mi) horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and plate movements.
Scientists have developed a theory–called plate tectonics–that explains the locations of volcanoes and their relationship to other large-scale geologic features. The plates move so the energy is released, causing the volcano to explode.
Science and the Environment
The incoming radiation is visible and ultraviolet light. The outgoing radiation is infrared light. The so-called Greenhouse gases (carbon dioxide, chlorofluorocarbons or CFCs, and methane) in the atmosphere strongly absorb infrared radiation, which is converted into heat energy. The relative proportions of these gases and their contribution to global warming is roughly 50% for carbon dioxide, and 25% each for the other two. If there were an increase in the concentration of these gases, more infrared radiation would be absorbed, causing a gradual increase in temperature, or a greenhouse effect.
{culprits (cause of the problem).} The major causes of the greenhouse effect are
•the burning of fossil fuels releasing carbon dioxide,
•deforestation, and
•other air pollutants such as methane and chlorofluorocarbons.
The major known consequences of the greenhouse effect are:
1.Rising sea levels
2.Potential ecological problems
3.Increased environmental problems