Science - Fossils yr 10

So far it includes lesson 1.1

What is a fossil

preserved evidence in rocks or soil of organisms that once existed on earth

How common is fossilisation?

very rare

What is a fossil

preserved evidence in rocks or soil of organisms that once existed on earth

How common is fossilisation?

very rare

What are the conditions for fossilisation

1. Quick burial in sediment - mud, sand, tar, amber

2. usually in/near water (though not always)

3. ONLY viable in sedimentary rock

4. Organisms with hard parts like bones or shells are more likely to fossilise successfully (as soft tissue decays quickly)

Why does soft tissue decay quickly

Its mostly made of proteins + other complex organic molecules which are easily broken down by bacteria + other decomposers, especially in warm/moist environments

Why fossils usually form in/near water

because water promotes rapid burial which allows the organism to be preserved and protects from scavengers/oxygen/bacteria (aka fulfils appropriate conditions for fossilisation).

What is a scientific model

A visual/physical representation of a concept/object that is too complex or small/large to create a real version of.

index fossils

used to compare the ages of strata in different locations

conditions for a species to be used as an index fossil

Must be widespread, have been abundant, have lived in a narrow period of time, and be easily identified

law of superposition

rock layers form parallel to the earth, deeper rock layers are older than superficial ones

the law of cross-cutting relationships

any rock layer that cuts across another is younger than those layers

the law of correlation

rock layers with the same index fossils in them are the same age

radioactive decay

absolute dating method

Definition of evolution

The process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth

How an original fossil forms

part of the organism is preserved, the chemical composition same as when it was alive, proteins within the orgs 'living’ bone decay, leaving behind minerals as hard but brittle bones

How carbon film fossils form

organism is buried, sediment piles up subjecting the organism to pressure and heat, gas + liquids are forced from it + a film of carbon forming a silhouette is left

What is an indirect fossil

No parts of fossil but evidence that it existed, e.g preserved footprints, burrow

What is relative dating

compares the age of one fossil/rock to another to determine which is older. Uses index fossils

What is absolute dating

Gives the actual age of rock (in yrs). Two types are radioactive dating and tree ring dating.

what is carbon-14 dating

uses half lives to date fossils that are less than 50,000 years old

what did lamarck think about evolution

‘evolution by inheritance of acquired characteristics’ (organisms are able to pass acquired features onto their offspring, offering them an advantage over others)

What did Darwin+Wallace think about evolution

‘evolution by natural selection’ (acquired features arent passed on, those BORN with features giving them survival advantages pass them onto their offspring)

what drives evolution

natural selection

Necessary conditions for natural selection

• variation between members of the population (must have better features for survival)

• selection pressure in the environment (feature of environment that gives some a competitive advantage)

• competition for fixed resources (food, water, shelter, mates)

• best suited reproduce more offspring + greater number of organisms in the next gen have this feature

• population slowly changes over many generations (repeats other steps)

How the fossil record (e.g horse fossils) provide evidence for evolution

Because they provide evidence for the existence of organisms that dont exist today, allows to see the sequence of evolution (orgs become more complex over time)

How transitional fossils provide evidence for evolution

show the ‘transitional stage’ as an animal transitions from one type of animal to another and has characteristics from both (archeopteryx is a mix between reptile and bird) through evolution, showing how organisms change over time

How comparative anatomy provides evidence for evolution

similar structures common to many animals (e.g pentadactyl limb, or five fingers) that have been inherited from a common ancestor

How DNA sequences provide evidence for evolution

shows how we all inherited some DNA from a common ancestor, so the more DNA you share with a species the more recent your common ancestor (eg humans and chips share 96-99% DNA, meaning our common ancestor was very recent

Similarities in present day organisms

1. there are common shapes and features that have developed through evolution and are shared across species due to needing to solve a common problem (analogous structures), e.g dolphins and sharks

2. common features inherited from a common ancestor in the ancient past like similar chemistry across all organisms (DNA and proteins), are all cellular (have cell/s)

Example of evolution in action via natural selection

• Peppered moths, black ones were very rare until industrial revolution. Factories were built and a dark smoke covered nearby countryside (so trees that were previously light + covered in lichens became dark). So the white moths stopped blending in and were spotted by birds. The black moths now blended in and survived + passed the black moth genes down

• bacteria exposed to antibiotics

example of human impact on natural selection

use of anitbiotics in human/veterinary medicine, peppered moths

What is the carbon cycle

theres carbon in the atmosphere and the air → plants take in the carbon → animals eat the plants → animals breath the carbon out → plants and humans die and the carbon goes back into the soil → plants grow from the dirt

What is the greenhouse effect

natural process that warms the earths surface. Some of the suns energy is absorbed, warming the planet. Earth then emits heat as infrared radiation. Greenhouse gases (CO2, methane) in atmosphere trap some of this heat, which keeps the planet warm enough to support life.

What is global warming/enhanced greenhouse effect

long term increase in earths average surface temp due to human activities.

What causes the enhanced greenhouse effect

human activities, primarily greenhouse gas emissions from industrial processes, so more heat is trapped and earths temp rises (global warming)

Impacts + evidence for enhanced greenhouse effect

global temp increase (global warming) leading to melting ice caps, rising sea levels and extreme weather events

how does global warming create extreme weather events

increased air + ocean temp affects water cycle, shifts weather patters and melts land ice, which are all things that make extreme weather worse

example of method of generating electricity using renewable source, pros and cons

Wind turbines

Pros:

• completely renewable and doesnt emit greenhouse gases

• simple repairs

• no fossil fuels used

• low cost (wind is free)

Cons:

• heavily relies on weather conditions which are unpredictable (if there is no wind, no energy will be generated during that period)

Common forces

• gravity

• friction (static, which prevents motion, and kinetic, which resists ongoing motion)

• applied force (like pushing a box, force applied to something by another person/object)

• air resistance

• electromagnetic force (opposite charges attract, like charges repel)

Common forms of energy + when their highest (kinetic, gravitational, elastic)

• Kinetic (energy of motion, greatest when object is moving fastest)

• gravitational potential energy (stored energy, highest when an objects at the top of a hill)

• elastic potential energy (energy stored in stretched/compressed elastics and springs)

Newtons 1st law

Inertia - an object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force

What is inertia (newtons 1st law)

the tendency of an object to resist changes in its velocity, whether in motion or motionless

Newtons 2nd law

An object will accelerate in the direction of an unbalanced force acting upon it. The magnitude of its acceleration is proportionate to the mass of the object and the size of the force acting on it.

• Net force of an object = mass x acceleration

Newtons 3rd law

for every action force there is an equal and opposite reaction force

How does an airbag (in car) reduce injury (inc. newtons laws)

• 1st law: object in motion will stay in motion unless acted upon by an unbalanced force (airbag acts as a ‘safe’ unbalanced force to stop the motion, rather than something hard like window or steering wheel)

• 2nd law: airbag increases passengers ‘stopping time’ (aka acceleration), therefore reducing the force exerted on the passenger (an object’s acceleration is proportionate to the force exerted on them)

Why do cars crumple

crumple zone is meant to absorb the force of the crash and extend the stopping time (time over which deceleration takes place, therefore reducing the amount of force the occupants are subject to (newtons second law, the force on an object is proportional to their acceleration)

Why are bull bars on cars dangerous for pedestrians

Dont crumple, all forces from the collision are transmitted to the pedestrian

how do seatbelts increase safety for passengers (in a crash)

extend the passengers stopping time, therefore reducing the passengers inertia/force on them (exerts a safe ‘unbalanced force’ to stop their motion, reduces acceleration which reduces force on them bc force is proportionate to acceleration)

how to calculate distance with a speed/time graph

find the area under the lines

average speed formula

Average speed (km/h) = total distance / total time

Acceleration formula

average acceleration (m/s²)= final velocity - initial velocity / time

average velocity formula

average velocity (m/s) = displacement / time

speed vs velocity

speed is a measure of how fast something moves (scalar) whilst velocity is the speed at which something travels in one direction (vector)

How replacement (petrified) fossils form

parts of the organism are chemically changed into another over a long period of time (shells/skeletons are often replaced by silica)