Lecture 17 Flashcards
What are methods for linking past climates to biodiversity (2)?
- Geology- conditions when deposits laid down and dates (looking at the states of the rocks)
- Biological materials- fossils, e.g. crocodiles in the Arctic, Palm in Alaska, Elk in Darlington. So, have to assume that at some time in the past the climate was suitable for these species
When linking past climates to biodiversity what do you assume? Explain
Assume no change in environmental affinities- meaning we assume that these organisms still need the same conditions they did back then, so we assume that the conditions were like that when these fossils were laid down
Explain permafrost (what is it a great source for, where do you find it and why?)
Permafrost is a great source of ancient biological materials, so you find them in Siberia where the permafrost never disappeared- so it is quite common to find things such as mammoths
Give an example of when a woolly mammoth was found (where, from when, condition, what does this mean?)
Siberia swampy conditions and permafrost
43,000
Hair, footpads, tusks, bone and blood still intact
So, you can sequence their DNA
What is peat good for? Give an example
Good preservative of biological materials (also gives a good idea of what the environment was like when the sample began to persevere)
E.g.
Tollund man- Iron-age Dane ~400 BC, moss indicated early Iron age
What is Palynology? Why do we use it?
The study of pollen grains and other spores, especially as found in archaeological or geological deposits.
Pollen grains- resistant to corrosion and species specific (use the pollen found in peat to determine what the climate was like at the time e.g. the tollund man)
Deep sea Foraminifera are good for estimating past temperatures. Why is this?
Because they are small marine creatures which have shells and their physiology is effected by the temperature. If it is hot/ cold they coil different ways and so you can get a sample and see the proportions coiled either way and get an idea of the temperature from that.
>8-10 degrees = right hand coiling
<7 degrees =left hand coiling
When they die they fall to the bottom of the ocean and then you can look at the proportion of left and right coiling and you can reconstruct the temperature (work out a percentage)
How can beetles be used to say what the environment was like in the past?
Assemblage of beetle species in deposits can calculate mean temp.
We know what temperatures different species of beetle like and you can look at the composition of beetles in sediments (using earth cores- used in the small marine creatures as well) and you can roughly tell what the temperature was like- can date them using radiocarbon dating (C14) (radio carbon only goes back 50,000 years)
How can stable isotopes be used to see what past environments were like?
These are incorporated into the plant by photosynthesis and when the plant dies it begins to decay depending on the amount of radioactivity in the sample.
Stable isotopes don’t decay but differ physically e.g. in rate of diffusion
How can belmnites be used to work out what the temperature was like in the past?
The belmnites are cephalopods, type of extinct squid. They have calcium carbonate in their shell that contains oxygen in it, so you can look at the proportion of did oxygen atoms in the shells of these belmnites and work out the temperature. (Also, can use tree rings)
Give a brief historical record of what the temp changes over the last 40 my indicate
- Long history warm tropical/ semi-tropical climate then
- Lowering of temperature
- Temp cycles over past 1.6my, including successive glaciations
Explain what eccentricity is
Earth’s orbit around the sun is eccentric. Every 100,000 years the Earth goes from being more circular to being more oval. This is due to the gravitational interactions with Jupiter and Satin
What are the names of the three bits to the Croll-Milankovitch cycle?
. Eccentricity- 100,000 years
. Obliquity- 41,000 years
. Precession- 22,000 years
Explain what Obliquity is
Every 41,000- the amount of tilt the Earth has goes from about 22.1-24.5 degrees.
As obliquity increases the amplitude/ size of the seasonal cycle and insulation increases, meaning you get more sun in summer and less sun in winter when the tilt is high and vice versa
What is precession?
Every 22,000 years.
The direction the Earth points to in relation to fixed points in space. Points to the VEGA star on one side of its cycle and the POLE STAR on the other side of its cycle. This movement is due to the tidal forces that are exerted by the sun and moon on the Earth, both contribute roughly equally to this effect
