Yr10 Science Notes 2024 - Biology - Evolution PDF

**[Yr10 Science notes 2024 -- physics and biology]** **[Life Goes on (biology)]** [Evolution (evidence for evolution) ] **What is evolution**? Evolution can be described as a change in species over time (gradual, or slow) - It is not a belief system, it is a scientific concept it has no role...

**[Yr10 Science notes 2024 -- physics and biology]** **[Life Goes on (biology)]** [Evolution (evidence for evolution) ] **What is evolution**? Evolution can be described as a change in species over time (gradual, or slow) - It is not a belief system, it is a scientific concept it has no role in defining religion - evolution relies on there being genetic variation in a population which affects the physical characteristics of an organism - some of these characteristics may give the individual an advantage over other individual which they can then pass on to their offspring. **Evolution is defined as** any change in the heritable (something you inherit) traits within a population across generations **Evidence of evolution** - fossil records - age of earth - biogeography - comparative anatomy (how organs of a body are similar to other animals) - comparative embryology (how certain organismims have same embrio stage) - molecular biolgy **[Ev1 Fossil records ]** [What is a fossil?] a fossil is the remains or impression of a prehistoric plant or animal embedded in rock and preserved in petrified form. the fossil may be the whole body of the organism, part of it or traces of its activities such as burrows, tracks or dung [Fossil record ] it lists all the species of living organisms that have been found as fossils as well as their location and relative age. it can be thought as a timeline of each. not all organisms are represented equally in fossil record. fossils are only found in sedimentary rocks, and never in igneous or metamorphic rocks. [Palaeontology] Palaeontology is the scientific study of life of the geologic past that involves the analysis of plan and animal fossils, including those of which are microscopic size preserved in rocks, these professionals study the evolutionary history of life on Earth (the study of fossils) [Fossil formation] The process of formation of fossils is known as fossilisation, it requires the organism or its traces to be buried quickly so that weathering and total decomposition do not occur [Types of fossils ] **Original fossils**: these form when a part of organism or the whole organism is preserved with its chemical composition being about the same as when it was living **replacement fossils** : These form when a part of organism is chemically changed into another mineral. These take a long time to occur, therefore they date back to over 60 million years ago. Generally, calcium carbonate found in shells and skeleton bones is replaced by silicon dioxide or opal **indirect fossils:** these are not part of the organism itself but are preserved remains of things such as imprints of the body. **Carbon film fossils:** They occur when the dead body partially decays and leaves a thin balck deposit of carbon (carbon imprints) **pseudo fossils:** sometimes watery solutions of various minerals speed through the sediments and it takes the shape of some plant part or animal. Their study shows that they are neither plants nor animals. **Index fossils:** index fossils are those that are used to define periods of geologic time a good index fossil is on with five characteristics 1. it is distinctive 2. globally widespread 3. abundant 4. limited to a particular geologic time 5. is robust and preserves well. **Transitional fossils:** A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. This is especially important where the descendant group is sharply differentiated by gross anatomy and mode of living from the ancestral group. **Dating fossils** there are two main ways in which the age of fossils is estimated 1. relative dating 2. absolute dating Relative dating is used to determine the relative age of a fossil. As the layers of sedimentary rock are usually arranged in the othe order they were deposited, the position or location of a fossil in the strata, or layers, of rock gives an indication of the time in which it lived. Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes either within the fossil or more often the rocks associated with it. **[Ev2 Age of Earth]** the age of the earth (4.5 billion years) is considered an evidence or evolution because the vast amount of time that Earth has existed allows for the gradual processes of evolution to occur. The geological timescale provides compelling evidence for evolution by showcasing the long history of Earth and the gradual changes that have occurred over billions of years. The timescale divides Earths history into several hierarchical segments from eons to eras, periods, epochs, and ages. Aspects to be considered in support of age of earth as an evidence of evolution 1. stratigraphy and rock layers 2. index fossils 3. radiometirc dating 4. geoglical events and enviromental changes **Stratigraphy and rock layers** the study of rock layers, known as stratigraphy, reveals a sequential record of Earths history. differnt layers represent different time periods, with old er rocks found at the bottom and younger rocks on top. fossils found in these rock laters show a progression of life forms over time, reflecting evolutionary changes. **Radiometric dating** radiometric dating techniques, such as carbon dating and potassium-argon dating, allow scientists to determine the absolute ages of rocks and fossils. By measuring the decay of radioactive isotopes in a sample, researchers can calculate the age of the material. These dating methods have consistently shows that earth is approximately 4.5 billion years old. **Geological events and environmental changes** The geological timescale also record significant events in earths history, such as mass extinctions, volcanic eruptions, and changes in climate. These events have influenced the evolution of life forms by creating new habitats, altering ecosystems, and driving adaptations in species. the long timescale allows for organisms to adapt to changing environments and diversity over time **Ev3 Biographical patterns** biogeography is the study of the distribution of living things and how they are affected by abiotic factors like oceans, rivers, mountains, valleys, and climate. The presence of related organisms across continents indicates when these organisms may hav evolved **Ev4 comparative anatomy** - comparative anatomy is the study of similarities and differences in body structures. - similarities are used to determine the evolutionary relationships between different types of living things - the more similar structure, the more closely related they are - the best example of comparative anatomy is in the limbs of vertebrates. The limb has been adapted by evolution fo ruse in different enviroments. Comparative Anatomy \| CK-12 Foundation [Homology ] homology refers to an anatomical feature possessed by an ancestor that has subsequently been modified by its descendants for a specific function. [Analogous organs ] analogous organs are the organs of different animals having different anatomy but doing similar functions or physiology, Example: wings of butterfly and flies, flippers of dolphin and penguin. they are a result of convergent evolution. [Vestigial structures ] - as evolution progresses, some structures get side-lined as they are not longer of use. These are known as vestigial strucures. - The coccyx is a much-reduced version of an ancestrail tail, whcih was formerly adaped to aid balance and climbing. - Another vestigial structure in humans is the appendix[.] **Ev5 Comparative embryology** comparative embryology is the study of the similarities and differences in the embryos of different species. similarities in embryos are likely to be evidence of common ancestry. The stages of development for say, a pig, and a human are the same (to a point). the presence of such similar genes doing similar things across such a wide range of organisms is best explained by them descending from a once common ancestor. **Ev6 Molecular biology** evidence of a common ancestor for all of life is reflected in the universality of DNA as the generic material and in the near universality of the genetic code and the way in which DNA is replicated and expressed. Proteins in all organisms are invariably composed of the same set of 20 amino acids. humans and chimpanzees share 96% of their DNA sequence. **Convergent evolution** - occurs when organisms become superficially similar because they live in similar environments or have a similar habitat or lifestyle **Divergent evolution** - Divergent evolution is the development of different species from a common ancestor. It occurs due to a process called adaptive radiation. - Scientists use fossil evidence, radiometric dating and DNA sequencing to work out when different groups diverged from a common ancestor. **Speciation** - The process of forming new species [Theories ] **Jean Baptiste Lamarck (1744 -- 1829)** - believed that living things evolved in a continuously upwards direction, from dead matter, through simple to more complex forms. - organisms alter their behaviour in response to environmental change - their changed behaviour, in turn, modified their organs, and their offspring inherited those improved structures **George Cuvier (1769 -- 1832)** - founding father of palaeontology - established the branch of comparative anatomy - disregarded lamarcks theory of evolution and believed in theory of catastrophism - violent and sudden natural catastrophes such as great floods and the rapid formation of major mountain claims resulted in extinction of plants and animals. **Charles Darwin** - proposed the theory of biological evolution by natural selection. - wrote 'origin of species' to explain how life forms change over time **the main points** - more organisms are born than can survive - within a population there is variation - those with favourable features survive by natural selection and reproduce offspring - over time the population change so that the favourable features become more common. this theory got rejected as he was unable to explain how evolution occurs, thats because he knew nothing about genes. As a result, he didn\'t know how characterises are past from parents to offspring, let alone how they could change over time. But his theory got accepted once he passed away **Alfred wallace (1823 - 1913)** he co discovered with charles darwin the theory of evolution by natural selecction he is one of the founders of the modern field of biogeography **Natural selection**  the theory of evolution relates to natural selection. For example, evolving long necks has enabled giraffes to feed on leaves that others can\'t reach, giving them a competitive advantage. Thanks to a better food source, those with longer necks were able to survive to reproduce and so pass on the characteristic to the next generation. [organisms characteristics ] **[Heredity]** the passing of characteristics from parents to children (offspring) through the process of reproduction heritable characteristics are also called traits **Acquired traits** - these are some variations - acquired traits develop due to the effects of environmental factors, use and disguise of organs and special efforts - these traits develop throughout the lifetime of an individual, and die with death of that individual - example-learning of dance, music etc and muscular body of a wrestler **Inherited traits** - these are genetic variations - inherited traits develop due to reshuffling of genetic material and mutations - these traits are transferred by the parents to their offspring these dont die bu are passed on to the next generation - example - attached or free earlobe and curly hair [DNA=Deoxyribonucleic acid] [DNA] - DNA is a biomolecule that is inherited from our parents. - DNA is made up of smaller sections called genes - DNA stands for deoxyribonucleic acid - it is found in nucleus of cells - each DNA molecule is tightly wound into a strand called a chromosome. - sections of DNA are called genes - humans have about 20000 genes - every cell in the body has the same DNA, cells are differnt however, as some genes are active while others are not **What does DNA do?** DNA is a code for making proteins it also contains the instructions needed for an organism to develop, survive and reproduce. **Structure of DNA** the first scientists to accurately describe the structure of DNA are **James Watson and Francis Crick** **Francis Crick and james watson Model of DNA** - the DNA has a double helix structure. The 2 strand are anti parallel which means they run in opposite directions. - the outside of the DNA is made of alternate sugar and phosphate molecules. The inside is made up of 3 different types of base molecule - A - Adenine - T - Thymine - G - Guanine - C - Cytosine sugar and phosphate molecules make the backbone of DNA. **[Nucleotides ]** - the sugar phosphate backbone, together with the base is called a nucleotide - there are 4 different types of nucleotides that make up DNA - Adenine alwyas pair (bonds) with Thymine - Cytosine always pairs with guanine - A=T ---\> hydrogen bonds (2 hydrogen bonds between A and T) - G=C ---\> hydrogen bonds (3 hydrogen bonds between G and C) **[Proteins ]** - proteins interact with other proteins to make things like eye pigmentation and all of your other characteristics - proteins are the "workhorse" molecules of lied, taking part in essentially every structure and activity of life. **[Genes ]** - genes are the units of heredity - they hold the information that passes on genetic traits from our parents. - one molecule of DNA (chromosome) has 1000s of genes - humans have about 20000 genes - In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA. **[Gregor Model ]** discovered principles of inheritance, experimented on yellow and green pea plants **[Chromosomes and DNA]** DNA is found in the nucleus of plant, animal and fungal cells. It is packaged into threadlike structures called chromosomes. Chromosomes become visible during cell division. Each chromosome is one very long DNA molecule with associated proteins. During cell division the chromosomes are visible as two parallel strands called chromatids joined together at the centromere. One chromatid from each chromosome will go to each new daughter cell formed during cell division. When the cell is not dividing the complex of DNA and proteins exists in a mass of very long, thin fibres not visible under a light microscope called chromatin. Chromatin packages the DNA into a smaller volume so it can fit into the nucleus and makes it easier for the DNA code to be used when it is needed to give the code to make particular proteins. A gene is one unit of hereditary information and occupies a specific section of a chromosome. Each gene has a particular DNA code. Researchers are identifying the genes on each chromosome, e.g. humans have 23 pairs of chromosomes and chromosome 1 (the largest) has more than 3000 genes along it. **[DNA replication]** DNA replication is one of the essential processes in a cell. During the replication process, the DNA molecule creates exact copies of its structure. The nucleotides of each strand provide the information needed to produce its new strand, and the two strands of DNA molecule have complementary base pairs. The two daughter cells that result have identical genetic information as the parent cell. DNA Replication and Repair [Origin of replication ] the site of origin of replication is the specific point on the DNA where replication begins. At this point, the two strands open and spearat, generating the replication fork [An Unwinding of DNA molecule ] the helicase enzyme binds to the replication sites origin, helicase is an enzyme that separates the two strands of DNA. Topoisomerase is an enzyme that unwinds the double helix above the replication fork and eliminates the twists throughout the process. The separated DNA strands each act as ea template. [Formation of RNA primer ] An RNA primer is a short RNA nucleotide segment. The primer is made by the DNA template close to replication sites origin. - also a nucleic acid (RNA = ribonucleic acid) the base pairs of RNA is A, U, C, G, where: - A binds with U (2 hydrogen bonds) - C binds with G (3 hydrogen bonds) - (there is no thymine, U replaces T) - U - uracil  [Synthesis of a new complementary strand from the parent strand] After the RNA primer is created, nucleotides are added using the enzyme DNA polymerase, and a new complementary strand of DNA is created from each parent strand. It is a unidirectional synthesis. In one strand, the daughter strand is synthesised as a continuous strand known as the leading strand. Short DNA fragments are produced on the other strand, which is referred to as the lagging strand. Okazaki fragments are the short segments of deoxyribonucleotides which are formed at the lagging strand during replication. These DNA fragments are linked by the enzyme called ligaes Replication comes to a stop when the replication forks on both sides meet at a location known as the terminus, which is located opposite the replication sites origin. [Significance of DNA] - DNA is the genetic material that allows genetic information to be passed down from one generation to the next - the information contained in DNA is necessary for the formation of proteins. - DNA controls an organisms development process and life activities. [Reproduction and Cell division ] reproduction is a characteristic of living things to ensure the continuation of a species Cells need to divide for your body to grow and for body tissue such as skin to continuously renew itself.  **[Asexual reproduction ]** Only needs one parent cell. Offspring are genetically identical to the parent cell Examples: - binary fission - budding **[Sexual reproduction ]** Two parent cells are needed. Offspring are not genetically identical to the parent cell. Occurs via fertilisation These parent cells are special sex cells, known as **gametes**,** **and each holds half of the genetic information of their parent. Male gametes are known as **sperm** and female gametes are known as eggs, or **ova** When the two gametes fuse a **zygote** is formed, in a process known as **fertilization***.* The offspring hold a full complement of genetic information -- half from the male and half from the female. [Human karyotype ] A karyotype is an individuals complete set of chromosomes In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46 22 of these pairs, called autosomes, look the same in both males and gemales. The 23rd pair, the sex chromosomes, differ between males and females the most common karyotypes for a femail contain two X chromosomes and are denoted for the sex XX. Males usualy have both an X and a Y chromosome, denoted for the sex XY [Karyotyping ] - karyotyping is the process of pairing and ordering all the chromosomes of an organism, thus providing a genome wide snapshot of an individual's chromosomes. - Karyotypes can reveal changes in chromosome number associated with aneuploid conditions, such as trisomy 21 (down syndrome) careful analysis of karyotypes can also reveal more subtle structural changes, such as chromosomal deletions, duplications, translocations, or inversions. - In fact, as medical genetics becomes increasingly integrated with clinical medicine, karyotypes are becoming a source of diagnostic information for specific birth defects, genetic disorders, and even cancers. [Down syndrome - trisomy 21] sometimes, when the egg and sperm are forming, the chromosome pairs do not separate in the usual way. The result is an egg or sperm cell that has only 22 chromosomes while others have 24 chromosomes. If an egg or sperm carrying 24 chromosomes combine with an egg or sperm carrying the usual 23 chromises, the result would be a person with 47 chromosomes in body cells instead of the usual 46 - down syndrome is the most common chromosome condition that babies are born with - people with down syndrome usually have distinctive facial features, some learning disability and may have heart or digestive tract concerns - down syndrome is caused by having an extra copy of chromosome number 21 [Sex cells] sex cells are called gametes sex cells are different to other cells and only have 23 chromosomes. sex cells are the cells which combine sexual reproduction to produce the first cell of an individual (known as a zygote) [Haploid vs diploid cells] **Haploid cells:** cells with only one set of chromosomes (one gene for each trait) are haploid - symbolised by N - all gametes are haploid - haploid cells are the result of meiosis **Diploid cells:** cells having homologous chromosomes (two genes for each trait) are diploid - symbolised by 2N - all somatic cells are diploid - diploid cells are created through mitosis. [The male reproductive system] A diagram of the reproductive system Description automatically generated **Scrotum:** The scrotum is responsible for protecting the testes. It helps with the thermoregulation of the testicles. It keeps the temperature of the testis several degrees below the average body temperature, which is an essential factor for sperm production. **Testis:** The testes are responsible for making sperm, and are also involved in producing a hormone called testosterone **Penis:** The penis is the male organ used for urination and sexual intercourse. The penis is located above the scrotum. **Prostate gland:** The prostates most important function is the production of a fluid that, together with sperm cells from the testicles and fluids from other glands, makes up semen. **Seminal vesicles:** The two seminal vesicles are glands that produce the fluids that will turn into semen. **Vas deferens:** these are located in each testical. The job of these ducts is to move sperm away from its storage place in the testicle **Urethra:** This tube allows urine to pass outside the body. The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. [The female reproduction system]  **Ovary:** The function of an ovary is to produce Eggs (female gametes) **Fallopian tube:** fallopian tubes are an important passageway for an egg and a sperm to meet and for a fertilized egg (embryo) to make its way to your uterus. **Uterus:** this is where the fetus develops **Vagina:** It provides a passageway for blood and mucosal tissue from the uterus to leave the body during a menstrual period. It\'s where the penis is inserted during vaginal sex and it holds sperm until they pass into the uterus. It provides a passageway for childbirth. [Fertilisation ] Fertilisation also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or offspring **step 1:** sperm and the ovum (an egg cell released from the ovaries) meet in the fallopian tube **step 2:** one sperm breaks through the ovum membrane **step 3:** the ovum nucleus and the sperm nucleus combine and fertilisation occurs **step 4:** Once a sperm fertilises an ovum, it becomes a zygote (half its DNA come from one parent, half from the other) **[Cell division ]** [Mitosis ] mitosis is a process where a single cell divides into two identical daughter celss - during mitosis one cell divides once to form two identical cells. - The major purpose of mitosis is for growth adn to replace worn out cells. - If no corrected in time, mistakes made during mitosis can result in changes in the DNA, that can potentially lead to genetic disorders. there are 5 steps in mitosis prophase, metaphase, anaphase, and telophase **(PMAT)** **Prophase** - DNA supercoils and chromosomes condense - chromosomes are comprised of genetically identical sister chromatids, joined at a centromere. - Paired centrosomes move to the form of opposite poles of the cell and form microtubule spindle fibres - the nuclear membrane breaks down and the nucleus dissolves **Metaphase** - microtubule spindle fibres from both centrosomes connect to the centromere of each chromosome. - microtubule depolymerisation causes spindle fibres to shorter in length and contract - this causes chromosomes to align along the centre of the cell (equatorial plane or metaphase plate) **Anaphase** - continued contraction of the spindle fibres causes genetically identical sister chromatids to separate - once the chromatids separate, they are each considered an individual chromosome in their own right - the genetically identical chromosomes move to the opposite poles of the cell. **Telophase** - once the two chromosomes sets arrive at the poles, spindle fibres dissolve - chromosomes decondense (no longer visible under light microscope) - nuclear membranes reform around each chromosome set. along with telophase, the cell undergoes a separate process called cytokinesis that divides the cytoplas, of the parental cell into two daughter cells [Meiosis ] - meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. - this process is required to produce egg and sperm cells for sexual reporoduction. - In Meiosis, the parent cell undergoes on round of DNA replication followed by two separate cycles of nuclear divsion. The process results in four daughter cells that are haploid, which means they contain half the number of chromosomes of the diploid parent cell - the process is split into meiosis I and meiosis II, an dboth meitic divisions have multiple phases. - Meiosis I is a type of cell dividsion unique to germ cells, while meiosis II is similar to mitosis. [Mitosis vs meiosis ] Mitosis - is a type of cell division that occurs when a parent cell divides to produce 2 identical daughter cells. It keeps the chromosome numbers same. - this process is required for multiplication by all body cells except sex cells. - gives rise to diploid cells. (2n) Meiosis - is. type of cell division that reduces the number of chromosomes in the parent cell by half and produces 4 gamete cells. - this process is required to produce egg and sperm cells for sexual reproduction - give rise to haploid cells (n) **[Star wars (astronomy)]** [Models of the universe ] **What is cosmology** the science of the origin and development of the universe. Modern cosmology is dominated by the Big Bang theory, which brings together [observational](https://www.google.com/search?sca_esv=62a62a0f9d145edd&sxsrf=ADLYWIIDZHnVKU4UQB3MMNwZk2y18bUc6A:1727926549505&q=observational&si=ACC90nyj24cUGopiOVnGD91130XTEY-gEph3x7W_TQHdtwzXmP1FG1Dc4TJCUXVSLSkwEbLTRhwM-8s9xEncPEcT9aMpX_18hNx3QjM3JUAFohNaoSb-apQ%3D&expnd=1&sa=X&ved=2ahUKEwjLnbmBpPGIAxVQr1YBHVRvIcEQyecJegQIShAO) [astronomy](https://www.google.com/search?sca_esv=62a62a0f9d145edd&sxsrf=ADLYWIIDZHnVKU4UQB3MMNwZk2y18bUc6A:1727926549505&q=astronomy&si=ACC90nytWkp8tIhRuqKAL6XWXX-Nt_A_eLTqqPCJ55LJpMG3a8RDaKPX_DRKGSA-4TSAAtAaZJLYRi6zapw3q0_pmUSgVnBA-EpkYViDtjiX7SnA6znuZB0%3D&expnd=1&sa=X&ved=2ahUKEwjLnbmBpPGIAxVQr1YBHVRvIcEQyecJegQIShAP) and particle physics. **The planets of our solar system (order closest to sun)** - mercury - Venus - Earth - Mars - Jupiter - Saturn - Uranus - Neptune **The geocentric model** The geocentric model was developed by ancient Greek philosophers, most notably by Claudius Ptolemy in the 2nd century AD. It was widely accepted in Western thought for over a thousand years, and similar views were held in other ancient cultures. In the geocentric model, Earth is placed at the center of the universe, and all other celestial bodies, including the Sun, planets, and stars, revolve around it in circular orbits. [Structure of the model ] **Earth as the Center:** Earth is stationary and occupies a privileged, central position. The heavens, including the Sun, planets, and stars, move in perfect circles around the Earth. **Epicycles:** To account for the complex motions of the planets (such as retrograde motion, where planets seem to move backward), Ptolemy introduced epicycles, smaller circular orbits that the planets made while orbiting Earth. This model aligned with the anthropocentric view of the universe, where humanity and Earth held a special place. Over time, the complexity of epicycles needed to explain planetary movements increased, making the model cumbersome and increasingly inconsistent with observations. The retrograde motion of planets like Mars, where the planet appeared to move backward in the sky, could only be explained using complex systems of epicycles. **The heliocentric model** The heliocentric model was proposed by Nicolaus Copernicus in the 16th century in his work De revolutionibus orbium coelestium While the idea of a Sun-cantered system had ancient roots it was Copernicus who developed it systematically. In the heliocentric model, the Sun is placed at the center of the solar system, and the Earth, along with other planets, revolves around it. This model replaced the Earth-centered universe with a Sun-centered one. [Structure of the model ] **Sun as the Center:** The Sun is stationary, and planets, including Earth, orbit around it in circular or elliptical paths. **Earth's Motion:** The Earth rotates on its axis (explaining the daily rising and setting of the Sun) and revolves around the Sun (explaining the annual changes in the Sun's position and the seasons). A screenshot of a black and white screen Description automatically generated The heliocentric model has come to be universally accepted as the correct model, it is also simpler than the complexity of the geocentric model. Modern cosmology has further expanded the heliocentric view by recognizing that the Sun itself is not the center of the universe, but part of the Milky Way galaxy, which is just one of billions of galaxies in the observable universe. [Formation of the universe ] 4.6 billion years ---\> vast clouds of dust and gas left after formation of sun 10 million years later, gravity draws debris to form planetary embryos **[Big bang theory]** by edwin hubble He observed: - light emission spectrum of stars galaxis - galaxies are moving away from us. - distances between galaxies are increasing in all directions - universe is expanding 1. one singualrity infinitaly small, matter expandend along with space 2. gave rise to tiny particles ---\> Then atoms 3. reduction in temperature ---\> allowed atoms to collide and condense 4. nucleus fusion resulting in first stars, dyring stars released other gases, create new Nebulae made new stars (with heavy atoms) 5. complex atoms and debris from dying stars, create planets that revovle arounf their stars 6. planets formed galaxies **origin (1):** the big bang theory proposes that the universe began as a singularity, which is a point of infinite densitiy and temperature. This singularity contained all the matter and energy that would eventually form the universe **Expansion (2):** Around 13.8 billion years ago, this singularity underwent, a rapid expansion known as cosmic inflation During this period the universe expanded exponentially in a fraction of a second, leading to the cooling of energy into particles and the formation of matter **Formation of elements (3):** As the universe continued to expand and cool, the first protons and neutrons formed within milliseconds after the BIG BANG, these particles then combined to form the first atomic nuclei, such as hydrogen and helium **formation of atoms (4):** As the universe further cooled, electrons began to combine with the atomic nuclei's to form neutral atoms. This process, known as recombination, occured around 380,000 years after the big bang and marked the beginning of the "dark ages" of the universe **Cosmic microwave background radiation (5**): About 380,000 years after the big bang the universe had cooled enough for light to travel freely though space. This light known as the cosmic microwave background radiation (CMBR), provides strong evidence for the big bang theory and is observed as a faint glow throughout the universe **Formation of galaxies and stars (6):** Over billions of years, gravity caused matter to clump together, leading to the formation of galaxies and the cosmic microwave background radiation **Evidence Supporting the Big Bang:** - **Redshift** of distant galaxies (Hubble\'s Law): Galaxies appear to be moving away from us, indicating that the universe is expanding. - **Cosmic Microwave Background Radiation**: This remnant heat from the Big Bang is uniform across the sky, supporting the theory of an early, hot universe. - **Abundance of Light Elements**: The relative amounts of hydrogen, helium, and lithium in the universe match predictions made by the Big Bang nucleosynthesis mode **[The steady state theory ]** The Steady State theory, proposed by **Fred Hoyle** and others in the late 1940s, offers a contrasting view. According to this theory, the universe has no beginning or end and has always existed in a **constant state**. It suggests that as the universe expands, new matter is continuously created to keep the density of the universe constant. **Key Concepts:** - **Continuous Creation of Matter**: As galaxies move apart due to expansion, new matter is created to maintain a constant density in the universe. - **Eternal Universe**: The universe is infinitely old and unchanging on a large scale over time. While local changes occur (e.g., stars forming and dying), the overall structure remains the same. - **Perfect Cosmological Principle**: The universe is homogeneous and isotropic in space and time, meaning it looks the same everywhere and at all times. **Evidence Supporting the Steady State Theory:** - During the early mid-20th century, **redshift** and **expansion** were consistent with this theory. It offered an alternative to the Big Bang, avoiding the need for a beginning. **[The concept of the expanding universe]** The concept of an expanding universe refers to the idea that the space between galaxies is continuously stretching, causing galaxies to move away from each other over time. This expansion was first observed by Edwin Hubble in 1929 when he noticed that distant galaxies are redshifted, meaning their light is shifted to longer wavelengths, indicating they are moving away from us. The expansion of the universe implies that, in the past, all matter was much closer together, leading to the Big Bang theory. [Stars] **Sun:** the sun is the star of our solar system. The sun is the largest centre of mass within the solar system composed of hydrogen (74%) and helium (24%) with and few other elements (2%). These elements are going through nuclear fusion (not fusion which is what our nuclear reactors do) and cause an immense amount of energy to be released every second The sun goes through the life cycle like every other star within our universe. This life cycle shows how stars go through a birthing stage, warming, red giant, and then into a white dwarf. Our sun is approximately 4.6 billion years only and will take many more billions of years to change its state. **Constellations**: Are patterns and shapes (that humans project) onto the visible stars in space. Whilst some constellations go towards predicting people's future (Astrology -- no scientific backing) it was essential for many travellers in the past to guide themselves across oceans. **[Stars ]** **What makes a star?** Stars start as a vast cloud of dust ang gas. These molecular clouds can be as big as hundreds of light years and are cold, causing the gas to clump. This clump grows in its gravitational force, sometimes gathering more gas and dust, eventually causing the clump to collapse. The gas and dust interaction creates friction, and that is the beginning- a protostar (baby start) The energy from the initial collapse carries the start to begin with. Gravity is the source of pressure and temperature in the stars core that cause the nuclear fusion (hydrogen \> helium). This fusion then releases more energy over time and prevents the star from further collapse. The nuclear fusion of stars is what we call the main sequence of stars in which is the longest phase. The luminosity, size and temperature will slowly change over billions of years. These factors also determine how fast and bright the stars burn. Stars that are smaller will be burning longer, with less luminosity than larger mass stars. Larger stars burn quicker, sometimes only for a few million years. Some smaller stars will burn longer than the universe has existed for. The fuel of a star will eventually run out and with no nuclear fusion, the star goes into its next sequence. The outcome of the star (death) is related strongly to its mass. Low-mass stars will expand their atmosphere until it becomes a subgiant or giant star (e.g. our sun). Some can become unstable and pulsate. The star will then blow out its outer layers, creating a cloud of dust and gas called a planetary nebula. The remnants are called a white dwarf (size of Earth) that slowly cools. High mass stars go further. Their fusion creates the heavier elements such as oxygen and magnesium which become future fuel for the star. The core is stopped from collapsing and in a short time. The interaction between the nuclei and the core create a shock wave that results in a supernova, a huge explosion. The remnants of this are either a neutron star or black hole.  **[Properties of a Star -- brightness and colour ]** stars are celestial bodies that can vary significant in size, brightness and colour. these properties help astronomers classify and understand the nature of different stars **appearance** - **brightness**: some starts appear brighter due to their intrinsic luminosity, while others appear brighter because they are closer to the earth - **colour:** the colour of a star can range from blue to red, depending on its temperature and composition Examples of stars by colour - **Rigel**: located in the constellation Orion, Rigel is a blue star known for its high brightness and being one of the most luminous stars in the galaxy - **Betelgeuse**: Also in Orion, Betelgeuse is a red supergiant star, known for its distinct red hue and considerable size. [Brightness of stars] **absolute magnitude** absolute magnitude is a measure of a stars intrinsic brightness, representing how bright the star would appear if it were placed at a standard distance of 10 parsecs (32.6 light years) from earth. This measure allows astronomers to compare the true luminosities of stars, independent of their distance from us. - **Example**: A star with an absolute magnitude of 1 is brighter than one with an absolute magnitude of 5 **apparent magnitude** apparent magnitue measures how bright a star appears form earth which can be affected by both the stars intrinsic brightness and its distance from earth. - **example**: A star that is closer to earth may appear brighter than a more luminous colour and temperature the colour of a star provides insights into its surface temperature and spectral type. The spectral classification of stars ranges from type o (blue) to type M (red), with intermediate types being B, A, F, G and K - **Blue stars (type o)**: 25,000k or more. These are the hottest stars, often young and massive - **white stars (type A)**: 7,500-10,000k. Many bright stars visible to the naked eye belong to this category - **yellow stars (type g)**: 5,000 - 6000k. Our sun with a temperature of approximately 5,500k falls into this category - **Red stars (type m)** 2,000 - 3,500 K. these are cooler stars, often older and include many red giants and dwarf stars. The hertzprung - Russell (H-R) Diagram The H-R diagram, developed independently by ejnar Hertzpring and henry norris Russel between 1911 and 1913, is a pivotal tool in astronomy. It plots stars according to their absolute magnitude (or luminosity) against their spectral type (or colour) Key regions on the H-R diagram - **Main sequence:** the diagonal band where most stars, including the sun, are found stars here are in a stable phase of nuclear fusion, converting hydrogen into helium - **Giants and supergiants:** located above the main sequence, these stars are much larger and more luminous. They represent later stages of stellar evolution - **white dwarfs:** Found below the main sequence, these are small, hot stars that are remnants of low-to medium-star [Magnitude scale ] the magnitude scale is a logarithmic where a difference of 5 magnitudes corresponds to a brightness factor of 100. Lower magnitude numbers indicate brighter stars: - **Bright stars:** have lower magnitude numbers (e.g., -1, 0, 1). - **Faint stars:** Higher magnitude numbers (e.g. 5, 6, which are the limit of naked eye visibility under dark skies) [Skills] [Valid reliability- multiple repititives,consistently in data, removing outlines, calculating averages] [Independent variables-variable being changed] [Dependant variable- variable that is measured] [Control-variable that stays he same] [Table you have to do all the trials and average] [Graphs] [dependent variable(unit)] [Title] [ ] [scale] [Independent variable (unit)]