ESO 1. Science

Topic 1.  Vocabulary
GravityEvery object in the Universe exerts a force of attraction upon the objects around it. This force is known as gravity. The Earth is retained by the Sun because of the Sun's gravity; the Moon is retained by the Earth because of the Earth's gravity, etc.
BillionIn most English-speaking countries a billion equals one thousand million; you can write it as 109. Likewise, a trillion equals one million millions, and you can write it as 1012.
Light yearDistances in the Universe are huge, and so they are measured in huge units. A light year is a distance unit that equals about 9.5 trillion km. It is the distance covered by the light in one year.
Astronomical unitIt is another distance unit. It is the distance between the Sun and the Earth, and equals some 150 million km.
Topic 1.  Galaxies and Clusters

The Universe is about 14 billion years old, and is formed by more than 100 billion galaxies. A galaxy is a huge system of stars, interstellar gas and dust. Typical galaxies contain from ten million to one trillion stars, all orbiting a common centre of gravity. Some galaxies are elliptical shape, some are spiral, others are irregular. Galaxies are usually separated from others by distances on the order of millions of light years. Groups of galaxies gravitationally attracted between themselves are called galactic clusters.

The Solar System is located in the Milky Way galaxy, a spiral galaxy with a diameter estimated at about 100,000 light years, containing approximately 200 billion stars. The Milky Way belongs in a cluster of over 30 galaxies known as the Local Group. The galaxy of Andromeda is the nearest to the Milky Way and the biggest one in the Local Group.

The Solar System resides in one of the Milky Way's spiral arms, known as the Orion Arm, at about 27,000 light years from the galactic centre. Its speed is about 220 kilometres per second, and it completes one revolution every 226 million years.

Topic 1.  Stars

Stars are massive, glowing balls of hot gases, mostly hydrogen and helium. Some stars are alone in the sky (the Sun, the North Star), others have companions (Sirius, which is a binary star system, and Alpha Centauri, which is a ternary star system). The nearest star to the Sun is Alpha Centauri C or Proxima Centauri. The brightest star in the Northern hemisphere's night sky is Sirius.

Not all stars are the same: stars come in all sizes, brightnesses, temperatures and colours:

  • The colour of a star is due to its temperature. A blue or white star is hotter than a yellow star, which is hotter than a red star.
  • The brightness of a star depends on two factors: (a) its distance from us and (b) its luminosity: how much energy it puts out in a given time, which, in turn, depends on its size. Think on a street lamp, which puts out more light than a hand torch. That is, the street lamp is more luminous. But if that street lamp is 1 km away from you, it will not be as bright, because light intensity decreases with distance. In this case, a hand torch held 10 m away from you would be brighter than the street lamp. The same is true for stars.
Topic 1.  Constellations

Constellations are groups of stars visibly related to each other in a particular pattern. Some well known constellations contain familiar patterns of bright stars. Examples are Ursa Major (containing the Big Dipper or Plough), Orion (that resembles the figure of a hunter) and Cassiopeia (with the shape of a "W"). The stars of a constellation, although appearing to be very near, may be millions LY away one to another.

Topic 1.  The Solar System

The Solar System is the stellar system formed by the Sun and the group of celestial objects gravitationally bound to it:

  • the eight planets and their 162 known moons,
  • five dwarf planets and their six known moons, and
  • thousands of small solar system bodies (SSSB).

The Sun is the main component of the Solar System, a star that contains 99.9% of the Solar System's mass. The Sun releases enormous amounts of energy in the form of electromagnetic radiation, which includes visible radiation (light), ultraviolet radiation and infrared radiation.

The planets are the biggest objects orbiting the Sun. Their orbit is almost circular. In order of their distances from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The four inner planets are small and rocky planets; the four outer planets are gaseous giant planets with a small rocky core. All planets but the two first are orbited by natural satellites (usually called "moons"). The planets, with the exception of Earth, are named after gods and goddesses from Greco-Roman mythology. The following table shows some major magnitudes measured relative to the Earth:

Diameter (relative to the Earth)Mass (relative to the Earth)Distance to the Sun (in AU)Revolution period (in Earth's years)Rotation period (in Earth's days)Moons

The dwarf planets are also rocky objects orbiting the Sun, smaller than the planets, but bigger than asteroids. There are currently (20-sep-2008) five dwarf planets in the Solar System; the two best known of which are:

  • Ceres, formerly considered the Solar System's biggest asteroid;
  • Pluto, a trans-neptunian object formerly considered the Solar System's ninth planet;

The SSSBs comprise several types of celestial bodies, the best known of which are:

  • Asteroids = planetoids = minor planets. They're the smallest rocky bodies orbiting the Sun. Unlike planets and dwarf planets, they are not spherical, but irregularly shaped. Most of them occupy orbits between the ones of Mars and Jupiter, and make up the asteroid belt. The biggest asteroid is called Vesta.
  • Comets, very small icy trans-neptunian objects that orbit the Sun in very eccentric orbits. When a comet approaches the Sun, its icy surface begins to boil away, creating two long tails, one of gas and another of dust, which are often visible with the naked eye. Two well known comets are Halley and Hale-Bopp.
Presentation: Why the Moon?
Topic 2.  The International System of Units
[Source: Wikipedia]

The International System of Units (abbreviated SI from the French language name Système international d'unités) is the world's most widely used system of units. The SI was developed in 1960 and, with few exceptions, is used in every country in the world.

The SI base units for the seven primary quantities are:

Electric currentampereA
Amount of substancemolemol
Luminous intensitycandelacd

Symbols are written in lower case, except for symbols derived from the name of a person. For example, the unit of electric current is named after André-Marie Ampère, so its symbol is written "A", whereas the unit itself is written "ampere". The only exception is the litre, whose original symbol "l" is unsuitably similar to the numeral "1"; thus it is recommended that "L" be used instead.

Abbreviated symbols should not be pluralized: for example "25 kg", not "25 kgs".

Symbols do not have an appended period (.) unless at the end of a sentence.

A prefix may be added to units to produce a multiple of the original unit. All multiples are integer powers of ten. For example, kilo- denotes a multiple of a thousand and milli- denotes a multiple of a thousandth. The SI main prefixes are as follows:

Topic 2.  Quantities

Quantities are the measurable properties of the physical bodies. Some of the most important ones are the following:

MassIs the amount of matter in a body. Its unit in the SI is the kg.
VolumeTells how much space an object occupies. Its unit in the SI is the m3.
CapacityIs the amount of space that can be contained by a body. It is measured in L.
DensityExpresses how concentrated is the matter in a body, this is, how much matter is there in a given unit of volume in a body. It is always the same for the same type of substance, this is, it doesn't depend on the size of the object. Its unit in the SI is the kg/m3.
TemperatureIt is not a kind of energy but a measure of the amount of heat in a body. It depends on the movement of its particles: the quicker the movement, the higher the temperature. Its unit in the SI is the K, but is commonly expressed in °C or °F.
Topic 2.  Characteristics of Some of the Common Chemical Elements Found in the Earth's Crust
SymbolAtomic numberAtomic mass% in continental crustRequired for Life
Mind Map: Calcium
Topic 4.  The Water Cycle
What is it?

The water cycle, also known as the hydrological cycle, is the circulation of water between the different compartments or reservoirs of the Earth's Hydrosphere, involving changes in the physical state of water between liquid, solid, and gaseous phases. The water cycle is powered by the Sun's energy and the Earth's gravity.

The Earth's water cycle involves the following main physical processes:
EvaporationIs the transfer of water from bodies of surface water into the atmosphere. This transfer involves a change in the physical state of water from liquid to gaseous phases, powered mainly by the solar radiation. 90% of atmospheric water comes from evaporation.
EvapotranspirationIs the transfer of water from living beings into the atmosphere. This transfer involves a change in the physical state of water from liquid to gaseous phases, powered mainly by the solar radiation and the heat released by the metabolism of the living beings. 10% of atmospheric water comes from evapotranspiration.
CondensationIt takes place when water vapour in the air accumulates to form liquid water droplets in clouds and fog.
PrecipitationIs atmospheric moisture that has previously condensed (or solidified), falling to the surface of the Earth. This happens mostly as rainfall, but also as snow, hail, or fog.
Surface runoffIncludes the variety of ways by which land surface water moves down slope to the oceans: snowmelt runoff to streams, streamflow, riverflow… Water flowing in streams and rivers may be delayed for a time in lakes. Much of the precipitated water evaporates before reaching the ocean or infiltrates into the soil.
InfiltrationIs the transition of land surface water into the ground. The infiltration rate depends on soil or rock permeability. Infiltrated water may become part of the soil moisture or accumulate in aquifers: in this case it is called groundwater.
Groundwater flowIncludes the movement of groundwater in aquifers. Aquifers tend to move slowly, so the water may return as surface water (into rivers, lagoons, oceans or through springs) after thousands of years in some cases. Water returns to the land surface at lower elevation than where it infiltrated.
Absorption or drinkingAre the ways in which soil moisture or surface water is taken in by living beings.
Volume of water stored in the water cycle's reservoirs:
Volume (106 km3)Percent of total
Seas and oceans137097.25
Ice caps, glaciers and snow covers292
Soil moisture0.0650.005
Streams and rivers0.00170.0001
Living beings0.00060.00004
Average reservoir residence times:
Groundwater: deep10,000 years
Seas and oceans3,200 years
Groundwater: shallow100 to 200 years
Lakes50 to 100 years
Ice caps and glaciers20 to 100 years
Streams and rivers2 to 6 months
Seasonal snow covers2 to 6 months
Soil moisture1 to 2 months
Atmosphere9 days
Topic 5.  Rock Grains

Sedimentary rocks can be made up of clasts or detritus (rock grains) weathered from other rocks by river waters, wind, coastal sea waters, glaciers, living beings, etc. This kind of sedimentary rocks are called detrital rocks.

They're classified upon the grains that they are made up of. First up, grains may be all the same size, uniform, as in a sandstone, or different sizes, as in a conglomerate. Secondly, grains may be bigger or smaller. The following table shows roughly how rock grains are classified upon their size:

Clay< 0.004 mm
Silt< 0.06 mm
Sand< 2 mm
Gravel< 6 cm
Cobble< 25 cm
Boulders> 25 cm
Topic 5.  Mineral Lustre

The term lustre refers to the appearance of a mineral surface in reflected light. The main types of mineral lustre are the following:

VitreousTranslucentQuartz, Halite, Olivine
ResinousTranslucentYellow and red sphalerite varieties
GreasyVariableMilky quartz
SilkyVariableFibrous gypsum
PearlyPoorly translucentOrthoclase, Mica aggregates
Dull metallicOpaqueCinnabar aggregates
MetallicOpaquePyrite, Chalcopyrite, Magnetite
Topic 6.  Vocabulary
Levels of organization Matter in living beings is organized in a series of levels of increasing complexity, ranging from the atomic level to the multicellular level with tissues and organs. Only plants and animals reach the highest one, whereas bacteria stay at the unicellular level.
Bioelements The most abundant chemical elements in a livig being, which are not much the same ones that you can find in a rock. The top six are C, H, O, N, P, S, and they're called the primary bioelements.
Biomolecules The most abundant types of molecules in living beings are always the same ones, no matter if it is a bacterium or a human. They may be organic (with a skeleton of carbon atoms: carbohydrates, lipids, proteins, nucleic acids) or inorganic (without it: water, mineral salts).
Cell The basic unit of Life. If something is not made up of cells, then it is not a living being. Cells can reproduce and interact with their environment (exchanginng matter and energy, and being able to notice its features). All cells have a plasma membrane, some organelles and genetic material.
Prokaryotic / Eukaryotic Cells without a real nucleus (no nuclear membrane) are the first type. Cells with a real nucleus (genetic material enclosed in a nuclear membrane) are the second type. Bacteria and Archaea are prokayotes; Algae, Protozoa, Fungi, Plants and Animals are eukaryotes.
Tissues In multicellular beings there may be different types of cells, each type being specialized in an specific function, and having the specific shape that allows them to fulfill that function the best. Each of those types is called a cellular tissue; examples are the vascular tissue (plants) or the blood tissue (animals). One tissue may have several subtypes of cells (e.g. white blood cells and red blood cells).
Organs / Organ Systems There are some tasks in a multicellular being that must be achieved by cells of different kinds working together (such as pumping blood throughout the human body). In this case, cells of different tissues gather and make up an organ (epithelial, connective, muscle and adipose cells make up the heart). Several organs working together in a common general task make up an organ system (the heart and the blood vessels make up the circulatory system).
Autotrophs / Heterotrophs Or Producers and Consumers. The former don't feed off other living beings: they transform inorganic substances to produce the organic substances they need; plants and algae are autotrophs. The latter need to feed on other beings and then transform the organic substances they have eaten into their own organic substances (i.e.: your proteins come partly from the proteins in that beef-steak you ate yesterday); animals, fungi and protozoa are heterotrophs.
Topic 6.  Differences between Prokaryotic and Eukaryotic Cells
Size (diameter)1-10 µm10-100 µm
Number of organellesFewMany
OccurrenceBacteria & ArchaeaProtozoa, Algae, Fungi, Plants, Animals
Topic 6.  The Five Kingdoms

This is not the most modern way of classification of living beings, but still proves to be quite useful to understand and organise the huge diversity of the living beings:

Groups of organismsType of cellsOrganizationNutrition
MoneraBacteria and archaeaProkaryoticUnicellularBoth
 AlgaeEukaryoticUnicellular to multicellularAutotrophic
FungiYeasts, moulds, mushroomsEukaryoticUnicellular to multicellularHeterotrophic
PlantMosses, ferns, flowering plantsEukaryoticMulticellularAutotrophic
Mind Map: Common features to all cells
Topic 8.  Vocabulary: Types of Plants
BryophytesTerrestrial plants that lack a vascular system, are dependent on environmental moisture for reproductive and nutritive functions, and that disperse spores for reproduction. The group includes mosses, liverworts and hornworts.
TracheophytesPlants with a vascular system that helps them to stay upright and transports the sap, the plants' nutritive liquid mixture. The vascular system is made up of the vascular tissues xylem and phloem. The group includes pteridophytes and flowering plants.
PteridophytesTerrestrial plants with a vascular system that are dependent on environmental moisture for reproductive and nutritive functions and that disperse spores for reproduction. The group includes ferns and horsetails.
Flowering plantsOr seed plants. Plants with a vascular system that are not dependent on environmental moisture for reproductive and nutritive functions and that disperse seeds produced inside flowers for reproduction. The group includes gymnosperms and angiosperms.
GymnospermsVascular flowering plants in which the ovules are not protected by an ovary. As they don't have ovaries, they don't have fruits neither, but cones instead. Their flowers are not very conspicuous, as they lack petals and sepals. They are woody and most of them belong in the conifers (such as the pines, cedar-trees, fir-trees, spruces and cypresses).
AngiospermsA vascular flowering plant in which the ovules are enclosed inside protective ovaries and the seeds inside fruits. They use to have well-visible flowers that, when complete, are made up of sepals, petals, stamens and pistils. They can be herbaceous (like the poppy) or woody (like the oak).
Topic 8.  Vocabulary: Leaves
LeafIt is the photosynthesis and transpiration organ in plants. Its two main parts are usually the petiole (a slender stem that supports the blade) and the blade (the green and usually flat area, with a midrib and secondary veins). When they have one only blade, they are called "simple leaves", whereas if they have several leaflets (each one resembling a single leaf with its petiole and its blade) they are called "compound leaves". You can tell whether something is a leaf or just a leaflet by watching the stipules: two membranes that are always at the base of the leaf, and never in the base of a leaflet. Holm-oaks have simple leaves, while ash-trees have compound leaves.
PalmateCompound leaves can be palmate, resembling a hand, with the leaflets outspread.
PinnateCompound leaves can be pinnate, resembling a feather, with the leaflets arranged on both sides of a central axis.
WhorlTwo or more leaves or other structures surrounding a stem at the same point.
BractA leaf associated with the flowers or inflorescences of a plant. Bracts are usually different in appearance to the other leaves on the plant. The lime-tree has very conspicuous elongated, narrow and pale-green bracts.
InvolucreA whorl of bracts, often cup-like, at the base of a flower, an inflorescence or a fruit. Daisies have involucres at the base of their inflorescences, and oaks have involucres at the base of the acorns.
DeciduousTo fall off or shed seasonally; usually refers to the leaves of a plant. It's opposite to evergreen. A poplar has deciduous leaves, while a holm-oak is evergreen.
Mind Map: Dicotomous key of leaves
Mind Map: Mammals

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