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#~~8678.5# years ago


Quick note: The half life of C-14 is more commonly 5730 years, the value I will be using.

To find the age of an object with a radioactive element still present, we use this formula:
#t=(t_(1/2)ln(N_t/N_0))/-ln2#, where #t# is the age of the object, #t_(1/2)# is the half life of the element, #N_0# is the initial quantity of the element (usually 100), #N_t# is the remaining quantity of the element after time, and #ln# is the natural logarithm (base of #e#).

As you can see, we have every value except for #t#. Plug our known variables into the equation, and we get

Therefore the bones of the prehistoric man are roughly 8678.5 years old.


Using yeast to make bread dough rise.


During the process of respiration, organisms such as yeast break down molecules of sugar to make ATP. Wastes produced by respiration include carbon dioxide and water.

Yeast are capable of...

  1. alcohol fermentation, which does not depend on the presence of oxygen.

#Sugar -> ethanol + CO_2#

  1. aerobic respiration, which does depend on the presence of oxygen

#Sugar + O_2 -> CO_2 + H_2O#

Yeast evolved the ability to produce alcohol as a means to kill off other microbes with whom the yeast compete for food.

The yeast produce alcohol. The rising alcohol levels kill off their competition, and then the yeast can later "digest" the alcohol to produce the ATP they need for life processes.

This video shows an experiment conducted to determine the effect of altering the temperature on the rate of respiration in yeast.

Hope this helps!




Typically, in ecology we classify a large area with similar flora and fauna throughout its boundaries as a biome.

These biomes have a relatively similar climate and terrain throughout their “borders”. A biome is also generally a large area so they tend to be home to many, many species of similar plants and animals.

Keep in mind though, biome is a human classification. This means that even though biomes can generally be similar on Earth, they’re not all the same.

The map below shows one classification of biomes in Africa

What is the tundra?

Aron Z
Aron Z
Featured 2 weeks ago


The tundra is a biome characterized by large, frozen plains, with only very short vegetation.


This biome has very low temperatures, low levels of precipitation, and a very short growing season. Tundra biomes occur mostly at very high altitudes or at very northerly latitudes.

In the tundra, there is often a layer of permafrost (frozen soil) beneath the top layer of soil. Usually, the tundra only supports very small plants, and there are no trees. Because of this lack of plentiful vegetation, only a very small variety of animals can survive in the tundra.



enter image source here


heterozygous: Pp
2 different alleles (1 dominant, 1 recessive)

white flowers: pp
2 recessive alleles are needed for the flowers to be white - if the dominant allele is present, there can be no white flowers.

the crosses of a pp and Pp plant, shown in this Punnett square, are Pp, Pp, pp, and pp.


In Calvin cycle or dark reaction, sugars are formed by using the chemical energy of #ATP# and #NADPH# formed during light reaction.


Equation for dark reaction:

#3CO_2# + #6NADPH# + #9ATP to (CH_2O)_3# + #6NADPH# +
#9ADP# +# 9#Pi

Diagram of Calvin cycle:

enter image source here

Steps in Calvin Cycle:

1st step: Carbon fixation:

It refers to the initial incorporation of #CO_2# into organic material. We will follow #3# molecules of #CO_2# through the reaction because we want sugars(carbohydrates) as the end product of cycle. And for this, at least 3 molecules of #CO_2# are necessary.
#3# molecules of #CO_2#→ contain #3# C→ so at least they will give #1# carbohydrate molecule( a triose).

  • Calvin cycle begins by the reaction of CO2 with highly reactive phosphorylated five carbon-sugar named ribulose bisphosphate(RuBP).

  • This reaction is catalyzed by the enzyme ribulose bisphosphate carboxylase also known as Rubisco .

  • The product of this reaction is highly unstable six-carbon intermediate that immediately breaks into two molecules of three-carbon-compound named 3-phosphoglycerate(PGA).
  • The carbon that was originally a part of #CO_2# molecule is now a part of an organic compound which means carbon has been fixed .

2nd step: Reduction:

In this step, fixed carbon is reduced to energy rich G3P with the energy and reducing power of ATP and NADPH respectively.

  • Each molecule of PGA recieves an additional phosphate from ATP of light reaction and form 1,3-bisphosphoglycerate.

  • It is reduced to glyceraldehyde 3-phosphate(G3P) by recieving a pair of electrons donated from NADPH of light reactions.
    Actually G3P is the carbohydrate that is produced directly from Calvin cycle.

  • For every #3# molecules of #CO_2# entering the cycle and combining with #3# molecules of RuBp, #6# molecules of G3P are produced. But only #1# molecule of G3P can be counted as a net gain of carbohydrate.
    Because out of every #6# molecules of G3P formed, only one molecule leaves the cycle to be used by plants for making glucose and other carbohydrates; the other five molecules are recycled to regenerate the three molecules of five carbon RuBP, the #CO_2# acceptor.

3rd step: Regeneration of #CO_2# acceptor, RuBp:

  • Through a complex series of reactions, the carbon skeletons of five molecules of three-carbon G3P are rearranged into three molecules of five-carbon ribulose phosphate(RuP).

  • Each RuP is phosphorylated to RuBP. Again #3# molecules of ATP of light reactions are used for this phosphorylation of #3#

  • These RuBP are now prepared to recieve #CO_2# again, and the cycle continues.

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