Yr 10 Science Physics and Evolution Test Revision PDF

**Yr 10 Science Physics and Evolution Test Revision** **Physics** **[Newtons laws]** First Law: (Inertia) An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an unbalanced force. - **Balanced Force**: Equal forces in opposite directions...

**Yr 10 Science Physics and Evolution Test Revision** **Physics** **[Newtons laws]** First Law: (Inertia) An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an unbalanced force. - **Balanced Force**: Equal forces in opposite directions that produce no motion or constant velocity \*Arrow indicates force -- size shows amount - **Unbalanced Force:** Unequal opposite forces produce an unbalanced force causing an acceleration \*Things don't keep moving forever as there is almost always an unbalanced force acting upon it  **Inertia:** Is a property of an object that describes how much it will *resist change* to the *motion* of the object. \*More *mass* means more *inertia* Second Law:\ **F = ma** Third Law: For every action there is an equal and opposite reaction. - **Example 1** -- When a gun is fired, the bullet expels forward, and the shooter is pushed back by equal force both ways. - **Example 2** -- When you step off a boat, the boat pushes back, often causing you to fall in. Oh no.      **[Energy -- Kinetic and Potential Gravitational]** Kinetic Energy: The energy of motion -- anything moving has kinetic energy \*Greater mass and speed = greater kinetic energy **Equation:** **KE = 0.5mv^2^** - **Example 1** -- Find the kinetic energy of a 1000kg car travelling at 5m/s - **Example 2** -- Find the mass of a ball kicked with 40J at 10m/s Gravitational Potential Energy (GPE): a type of stored energy associated with objects above the ground. On Earth, we always have the force of gravity acting upon us. When we're above the earth's surface we have potential (stored) energy. \*Depends on mass and height above the ground - on earth **Equation:** **PE = mgh** **[The Law of Conservation of Energy]** "Energy cannot be *destroyed or created*, only *transferred or transformed* from one form to another" \*PE = KE **Example -** The amount of energy you start with must be the same as the amount you end with. **[Practice Questions]** 1. A 100g apple falls from a branch 5m above the ground. With what speed will it hit the ground If the air resistance could be ignored? 2. Dr Spook is the first human to set foot on an unexplored planet. He radios back to the mother ship that his weight is 525N on the surface of this planet. If Dr Spook's mass is 70kg, what is the gravitational acceleration of the surface of this new world? 3. **[Extra Notes]** - Weight = mass x gravity - Speed conversions:  **Evolution** **[Natural Selection]** - Process where an environmental factor impacts populations \*[Selective agent] = selects the characteristic that will survive - Results in more or less offspring from particular organisms - Organisms best suited to the environment survive and pass genes \*Survival of the fittest - Less adapted organisms produce less or not at all - [Selective agent:] may be a colour of fur, trait, mutation, adaptation - [Speciation:] the process by which one species splits into two separate ones Three steps: 1. Variation 2. Isolation 3. Selection Variation: - Natural selection depends on the variation of traits within a population - Genetic variation is caused by: mutation, random mating/fertilisation and crossing over in meiosis - Provides options for the species when an environment changes - Individual organisms may be wiped out - Favourable adaptations survive and continue species gene pool Isolation/Selection: - When two populations of species are separated, gene flow is stopped \*Two species → different selection pressures = become more different - Eventually become incapable of interbreeding, as are different species Reproductive Isolation: - Species might not be able to breed due to: - Courtship behaviour -- new breeding rituals - Breeding seasons -- breed at different times of year - Sterility -- breed sterile offspring **[Evolution]** - Evolution is often accepted because of the law of natural selection \*Natural selection is a mechanism of evolution - It is the clearest explanation for the diversity of organisms - Mutation causes variation - E.g. Sickle cell recessive alleles being passed on - Artificial selection is used for breeding - Producing desired characteristics in specific offspring - Faster form of evolution **[Evidence of Evolution]** May be in the form of: - Fossil record - Comparative anatomy - Comparative DNA and protein structure - Geographical distribution Fossils: **Definition** -- Remains or traces of organisms from a past geographical age embedded in rocks or other substances by natural processes - **Example --** footprints, imprints, faeces - Helps provide evidence, as it shows an increasing number of species upon earth - Supports evolution because you would expect biodiversity if species continually split into two or more species overtime - Shows increase in complexity of species has changed over geological time Comparative Anatomy: **Definition** -- Compares structures of living species and fossils - Homologous structures: structures with no apparent function and appear to reside from a past ancestor - Comparative embryology: Comparisons of vertebrae embryos show similarities in the early stages of development - Vertebrae embryos have structures that appear to be homologous on the basis of anatomy - The same gene has been produced but with different effects in two different species Comparative DNA: - All living cells have some basic DNA structure and use some genetic code - Even though organisms seem to be very different, they have large sections of identical DNA - Protein structure -- closely related species have more similarities in amino acid sequences in particular proteins Comparative Distribution: **Definition** -- Map of all the places where a species occurs - Many unique species occur on isolated islands \*Less connection = less gene flow - With evolution, expect to find unusual species on particular islands because isolation helps speciation to occur - Continents now separated by oceans contain identical fossil species as they were once connected in the past **[Extra Notes]** Example of natural selection: **Natural Selection in Peppered Moths**\ Peppered moths show natural selection through colour variation: some are light with black speckles, while others are entirely black. Before the Industrial Revolution, both types lived in rural and urban England. During the Revolution, pollution darkened city buildings with soot. Light-coloured moths became easy prey for birds, while black moths blended in, survived, and reproduced. Over time, the black variant became more common in industrial areas. **Natural Selection in Humans**\ Sickle-cell anaemia, caused by a gene mutation, affects red blood cells\' shape and oxygen-carrying ability. People with one sickle-cell allele (heterozygotes) are resistant to malaria, giving them a survival advantage in malaria-prone regions, where they pass on the allele to future generations. **Artificial Selection**\ Darwin noted that farmers selectively bred animals for desirable traits, a process he compared to natural selection. Unlike natural selection, which is driven by the environment and occurs slowly over generations, artificial selection is controlled by humans and can happen more quickly. For thousands of years, humans have bred plants and animals for traits like milk production, wool thickness, or meat yield. For example, Belgian Blue cattle are bred for higher meat production. - **Vestigial structures:** non-functional features fully developed and functioning in earlier species but serve little or no present purpose for an organism. Such as the human appendix or tonsils. - **Difference between homologous and vestigial structures:** Homologous structures are structures amongst two species that appear similar because they were developed from a common ancestor. For example a human limb and whale fin are homologous because the bones have the same general layout. Vestigial structures are ones that appear in a species but no longer serve a function. Homologous structures share an ancestor but serve a different function, but analogous structures serve a similar function but do not share an ancestor. Vestigial structures are traits that our ancestors needed but no longer serve a purpose in our environment. - **Selection pressures:** an evolutionary force that causes a particular phenotype to be more favourable in certain environmental conditions. Selective pressures are considered forces that drive evolution via natural selection. Some phenotypes are more favourable than others, depending on external conditions. Selection pressures are external agents which affect an organism\'s ability to survive in a given environment. Selection pressures can be negative (decreases the occurrence of a trait) or positive (increases the proportion of a trait).