Yr 10 Half Yearlys Flashcards
Fossil
are traces of past life preserved in soils or rocks
Palaeontology
is the study of past life
The fossil record
the fossil record is a record made consisting of all the fossils that have been discovered, together with their relative ages. Fossils are a rare occurrence and the fossil record is incomplete.
How do different preserving environments result in different types of fossil
Some environments suit the formation of fossils such as shallow lakes and seas. Some parts of organisms like bones and shells fossilise more readily than soft tissues and tiny bacteria.
Permafrost
near the Arctic Circle, the land is almost frozen. Bacteria and fungi that cause decay cannot grow if the temperature is below freezing.
Amber
amber is solid plant sap or gum. When amber sets and hardens, it can preserve whatever is entombed inside it.
Tar
tar pits occur when oil seeps out of the ground and onto the surface. Many animals such as mammoths and sabre-toothed cats became stuck in the sticky tar, leaving them to die there and become fossilised
Peat
the layers of peat can be very deep and oxygen and bacteria are often absent in the lowest layers. This gives the soft tissue trapped in these layers a chance of being preserved. The peat is generally acidic and this dissolves the hard minerals in the bone, making them very soft
Dry air
dry air dehydrates the soft tissue, which fossilised, and turns it into a ‘mummy’. The mummified skin then forms a mould in sediments.
Explain the fossil record being incomplete
due to the nature of many organisms (small and/or no hard parts) and the low chance of being fossilised after death, due to scavengers and being in the wrong place
Define relative dating
Relative dating is the process of determining if one rock or geologic event is older or younger than another, without knowing their specific ages.
How does relative dating work
compares the ages of one fossil or rock with another to determine which is older. The process relies on two assumptions: sedimentary rocks form in layers, fossils are the same age as the rocks in which they are found.
State the characteristics of index fossils
Index fossils are fossils used to define and identify geological periods
To be used as an index fossil, the species must have been fairly widespread, lived in a fairly narrow period of time, been abundant and been easy to identify. They can be used to accurately compare and date the ages of strata in different locations using relative dating.
Characteristics of index fossils such as trilobites and explain why these can date rock layers.
Trilobites evolve rapidly, and like other arthropods, trilobites serve as excellent index fossils, enabling geologists to date the age of the rocks in which they are found.
Define stratigraphy
the science of comparing rock layers (strata) to gain information about the history of the earth.
Explain how stratigraphy is based on the use of index fossils
Sediments fall due to gravity and form horizontal layers.
The materials the layers are made from can be studied and any fossils within these layers can be used to determine a relative age for the rocks.
Define absolute dating
the process of determining an age on a specified chronology.
Explain how radioactive decay is used to date rocks and fossils.
Some elements have isotopes which are radioactive so they release particles and energy in a steady stream to become stable in a process known as radioactive decay.
The half-life of an element is the time it takes for half of the radioactive sample to decay to a new element.
A sample of rock can be taken and analysed to compare the proportion of original radioactive particles to new particles it contains. Once this is measured we can use this to determine how long the sample has existed or its age.
Radioisotopes decay at a known rate and this rate of decay can be used to estimate how long ago a rock was layed down.
Outline the fossil history of the vertebrates, emphasising the stage when life spread from the oceans to the land.
Around 400 million years ago some vertebrates, such as fish, started developing limbs and other characteristics that allowed them to explore life on land. Lobed-finned fish is a transitional species that shows the link between fish and tetrapods (four-legged animals). It has special features that enable it to move from water to land.
Characteristics of lobe finned fish
Lobe-finned fish had bones in their fins similar to land animals, therefore some of these fish may have been able to pull themselves up onto land with their fins. A lobe-fined fish had a stalk-like feature that attached a fin to a body. This lobe fin allowed the organism to support its body and to crawl from the water to land. Its lungs also allowed the organism to breathe air when on land. Lobed-finned fish is a transitional species that shows the link between fish and tetrapods (four-legged animals).
Importance of lobed-finned fish
gave rise to tetrapods. transitional species
Newtons first law with example
Inertia:
an object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an unbalanced force. An example of this is when your body moves when the car turns a corner.
Newton’s second law
an object will accelerate in the direction of an unbalanced force acting upon it. The size of this acceleration depends upon the mass of the object and the size of the force. Force = Mass x acceleration.
Examples of Newtons 2nd law
A ball. A ball develops a certain amount of acceleration after being hit. The acceleration with which the ball moves is directly proportional to the force applied to it. This means that the harder you hit the ball, the faster it will move
