the use of Radio active substances

most radio isotopes are artifically made and over 1000 diffrent types can be prepared. they are used in industry and reasearch, and also have medical applications.
radioisotopes. are useful in many ways. they can be used as radioactive tracers to follow movment of  substandes through liquides. gamma radiation kills the micro organisims in food. it keeps it from spoling . however there has been much contraversy about the safty of food that has been treated this way.
naturaly occuring radioisotpes can be used to calculate the age of samples from archiological sites. teh radio isotope of carbon as an example occurs naturtl in the atmosphere as a component of carbon dioxide. during photo synthasis, plants take in carbon. including the radio isotope becomes part of the plants cell and parts of teh cells of those animals that consume the plats. when the plant dies it takes no more carbon 14. the half life for carbon 14 is 5730 years , it is possible to estimate teh age of a dead plant or animal by materials excavated from an archeolofical sites often include organic carbon. it is possivble to test how much radioactive carbon remains in teh samoples and from this infromation it can be calculated how old the samples are. this techniqe is called radio-carbon-dating.
radio active isotopes are also used in smoke detectors. soil analysis. pollution testing. mesuring the thickness of objects and arimology.

the life time of radio active particles.

most radio active substances have very lonbg lives we mesure the life time of radio active substances in units called half life. a half life is teh time it takes half of the radio active substance to be used up. a typical graph showing this is shown

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this is called expontential decay

the way a nuclear reaction works

slow nuetron
			     !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!           gammarays,	141
		 000    	!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!			56         barium nuclease
+ - - - - - >	0000 -----> NUCLEAR REACTION	
		 000	!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! fuery
	    uranium nucleas !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

schematic explarution
 
		    N-u
 		   /N-u
		  / N-u
                   N---U     N-u
N---> U---------N--U-----N-u
                   N---U     N-u
		 \ N-u
		  \N-u
	`	   N-u

gives off energy

by inserting control rods we can control how much energy is replaced
if control rods are inserted all teh way teh reaction is stopped because it absorbed all the nuetrons.

times are changing.

if you could travel back in time some 10 millions years. the plants and animals you would see living on the earthj would be very diffrent to those you have tonday. to gain some insight into what life was like 10 million years ago we need to look futher than rock.

the fossil record

a fossil is evidence of past life. fosils can be parts of an organisme sah as horns, teeth usallly when an organisem dies micro organesem is covers it shortly after then it is coverd by dirt mud sand or somthing else. the micro organisems that casue decay cannot work. this is becasuse there is no oxygen. over millions of years the material covering the dead organisem is compressedx and turned into rock. preserving the fossil within it.

for example a dinosore trach has been discorved in teh otway range, in southern victoria. by observing teh foot prints in the track palen toligest  can work out the size speed of the dinosar that made them.

dating fossils.
radioactive carbon dioxide is naturly present in air and living things are constantly incorperating a small amount of carbon into there body tissy, this ubtaj stios at death, after which the radio carbon in the organisem begus to slowly break down into its non radioactive form. by calculating the amount of radioactive carbon left in the body. it is possible to work out when the organisem died, this type of dating is called absolute dating. and can be used to caluclate the age of fossils that died thousands of years ago.
there is also another method scientist can use to calculate layers of rock were laid down first and tehn other things to assses them

recording change

the fossil record also gives evident that species have changfed along time and may show how new species arose.
the fossil sized skeleton at a bird shown below was found in  afganistan and has been dated to around 150 million years. if clearly shown below what was found in iraq and has been dated fir 1500 million years. it clearly shows features of all modern birds how ever it also has dinosour charachteristics, such as teeh claws on its wings and a long jointed bony tail. from this scientist have deduced the birds evolved from a dinosour ansestor. the evolution or change over time of other species can also be followed by studying the fossil record.

evidence that life may have exusted ib mars has been found inside a metior with microscopic fossics. and has been dated about 13000 years. examination of these slices of the metoratic under electronic microscope has suggested teh presance of micro fossils of singular cell organisems. each thing evolved into more complex and diverse organisems.
the earliest known fossiols have been found in greenland. they contain carbon from organisems that once lived and have been dated of 3800 million years ago.

questions

a time for contraversy

1. some were giant tortes, land iguanas, marine iguana
2. they awere herbavours, diffrent colours and markings bluinted nose and serrated teeth
3. becvause so he could colloect tnough evidence to prove his theory was true.
4. charles lyell belived that most land forms had formed slowley over time not as a result of catasroophies. thomas malthus suggested that these did not gro as fast as expected because of war famine and disease.
5.because wallice did not act on what he had found he dident present his theory to the world

Darwins findes

1. by depositing bird droppings with seeds in them
2. the thing unusual was that there were many diffrent types of finches
3.it is different by choosing the most suited to be breed and no others

natural Selection

1.i think that fittest in that phrase means most suited to survive in the modern world
2.that the rabits became more resistant to the virus and the virus has become less virulent

two diffrent thearies

1. need- somthing you accuire to survive
aqure- to gain
variation- diffrent types
extints- somthing that seizes
select- to choose
2. that natural selection is the process which evolution is made

3.horses 60 million years ago where alot smaller than the ones we see now

new species
1.the mutation or change of an organisem to a diffrent shape or size of body or body part though natural selection
2.
	a= yes
	b=yes
	c=no
	d=no
	e=yes
	f=yes

evidence for evolution

1	-fossil evidence
	-comperative anatomy
	-bio geography
	-compurative emlotology

2. the horse 60 million years ago was small and had feet suited for soft ground. 40 million years ago it grew a little bit bigger and had feet suited for forest. 30 million years ago the horse grew eaven more bigger from o.6m to 1m and had feet suited for prairies. nowadys it is 1.6 m and is suited for dry grassland
3. by the way their feet were made depending on how narrow and wide it was. was better suited for all types of lands
4.because on land there are tornadoes and wind and earthquakes that help preserve fossils.

newforms of evidence

1.that by seperating the parts of it then reforming them to create new organisems, or so called hybrids.
2. the double helix is heated to seperate teh single strands.
3. if there are no genetic simalarites the strand will no form a double helix, that would only happen if strands had genetic similarites
4.genetic similarites between evolved and non evolved animls and organisms also other bio chemical evidence for evolution.

how old are fossils 

the age of the earth has always intrigued scientits. one of the first attempts to calculate the age of the earth was made in 1715 by the english astronomer edmund halley. he recorded that oceans where once fresh water. and had gradully become salty because of salty rocks.if the age of the oceans could be found then this would give some idea of the age of the earth. other scientist tried to calclate teh age of the earth by estimating how long it would take sedimentry rocs to form. how ever sedimentry rocks from at diffrent rates in diffrent places on the earth. this led to in accurate estimates.

dating fossils

there are a number of radioactive substances that have proved reliavle in estimating the age of fossils. generally the uranium lead method is used for dating very old fossls while iadioctive potassium-argon has beed used to estimate the age of fossils from one million years to 500 million years old. scientist estimate the age of very old fossils from the ages of rocks near where they were discovered fossils are generally found in sedimentry rocks. and sedimentry rocks form from the sedimitey rock could give an incorrect age. for the fossil  lonsequentky the scientist look forr igneouse rocks which have formed near the sedimentry rock in which the fossil had used for dating, the scientist date many sample. of the igniues rocks and them found the average age which gives them an estimate of teh age of teh fossil,

radioactive dating

the discovery of radioactive dating was in 1900 provided a way of finding the age of the earth much more eaccuratly. uranium atoms give off energy and particles. and evently decay to lead atoms. this prcess is called radioactive decay. the age of the rock can be hound if the ratio of uranium atoms to lead atoms contains inturn is frustrated. the rate at which uranium decays is now known and assumed to have been constant throughout the life of the earth,.

radiocarbon dating

this method is used to date very young fossils and two other methods, dates the material in the fossil  iteself. this method has two advantages that are teh age of the fossil is mesured directly. radioactive carbon 14 is beuing fomed and broken down continually in the uper atmospher like normal carbon it joins with oxygen. to form carbon dioxide. thus radioation in the atmosphere is furly constant and scientist assume that thise ratio has remaind constant for hundreds and thousands of years.

geological theory

there are two basic principals

1. the principal of horzinatality whichc states all layers of rock are orignally laid down horziontally

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2.this principal is about the age of the fossils. it is stated younger fossils occur higher in the rock strata
older fossils occur futher down

main ideas
1. fossils are preserved remains of the past life on earth
2. generally only parts of the whole organisems found as fossil scientist have to infer the structre of the whole organisem from these parts
3.organisems that live in or around the water have greater chame of being fossilised
4.fossil may be found petrified carbonised as moulds or casts or preserved unalterd