OCR 2010 A2 Biology Unit 2 - Control, Genome and Environment

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Reply 1880

Falcon91

MadMaths

Can Some one Explain what is phylogentic species Concept???

See my post above on page 94 of this thread.

Reply 1881

ViolinGirl

MadMaths

Can Some one Explain what is phylogentic species Concept???

The phylogenetic species concept states that a species are a group of organisms with similar morphology, embryology, behaviour, physiology and occupy the same ecological niche.

It allows for species that produce asexually to be classified and it doesn't base its classification , as the biological species concept does on an the organisms being similar. As organisms can actually appear very different but still be part of the same species.

The phylogenetic concept classifies organisms according to evolutionary relationships, it is based on DNA, RNA and protein analysis, as well as further analysis of the base pairs that make up the genome of an organisms. Organisms that have haplotypes that are more similar than any other organisms ar eplaced in a group called a clade. Cladistics is a form of heirachical classification, computer programs can be used to assmble organisms into cladograms, and dendograms. These can be monophyletic- where the ancestral organism is shown and all the decendant species, or paraphyletic- where only the most recent ancestor is shown, and one or more of the clades are removed.

Reply 1882

ViolinGirl

Falcon91

Explain the term genetic code and transcription. :wink:

Yes. We are both online now :smile:

The genetic code refers to the sequence of nucleotide bases that make up a gene, these a triplet codes, they consist of 4 of the organic nitrogenous bases, A, T, C and G, that are grouped into 3, this enables for enough combinations of sequences to be made to code for each of the 20 naturally occuring amino acids in the body. The genetic code is degenerate so more than one code is present for the same amino acid, some of the codes do not code for polypeptides but indicate that it is the end of the chain, and it is widespread but not universal. This is useful for genetic engineering as it means that you can removed one gene from one organism place it in another and it will usually synthesise the same protein.
Transcription is the first stage of protein synthesis, this is where a single stranded mRNA copy of the DNA coding strand is made. This leaves the nucleus through the nuclear pore and attaches to a ribosome for the second stage of protein syntheisis, translation.

Describe the Chi squared test! :wink:

Hurry Falcon, hurry!

Reply 1883

ViolinGirl

ibysaiyan

Hey Violin waddup =} How is the revision kicking? :smile:

OK, except I don't think I will finish physics in time :frown:

Hows it going for you dude? :p:

And I keep thinking I don't know bio!

Reply 1884

uer23

are you guys covering the whole spec here ?

Reply 1885

ibysaiyan

ViolinGirl

OK, except I don't think I will finish physics in time :frown:

Hows it going for you dude? :p:

And I keep thinking I don't know bio!

same here I have lost that motivation(push) to do any reading :frown:

argh....

Reply 1886

ViolinGirl

uer23

are you guys covering the whole spec here ?

Whad'ya mean? :smile:

Reply 1887

aiden1234

ViolinGirl

I'll summarise it for you :smile:

Plants, like animals need to respond to the environment, to reduce the stress on them prevent them from being eaten, and allowing them to survive to reproductive age.

Tropisms- these are directional repsonses in which the direction of the response is governed by the direction of the external stimuli.

There are different types of tropisms:
1) Geotropism
2) phototropism
3) Thigmotropism
4) chemotropism

Plant responses are coordinated by hormones, but these are known as growth regulators as they are produced in various parts of plant tissue and not from endocrine glands.
Hormones are specific, only act on target cells.

The main hormones in plants:
-Auxins
-Cytokinins
-Gibberellins
-Abscinsic acid
-Ethene.

ahhh so do we have to know the actual effects of these hormones...or just like Auxins and Giberellins....and maybe Ethene? :confused:

Reply 1888

Falcon91

ViolinGirl

Describe the Chi squared test! :wink:

Hurry Falcon, hurry!

Lol

Chi squared is basically a way of working out whether there is a significant difference between the observed and expected results, thjis allows to to decide whether a hypothesis is avalid or not.

The hypothesis is called the null hyopthesis.

Chi Squared formula = The sum total of (o-e)^2/e for all classes

This value is then compared against a critical value, the degrees of freedom is equal to the number of classes - 1 (in biology this is usually 3 degrees of freedom). If chi squared is less than this critical value, then there is no significant difference between the observed and expected results and thus the null hyopthesis is accepted.

If chi squared is greater than the critical value, then there is a significant difference between the observed and expected results and so the null hypothesis is rejected.

Describe the concept of dominant and recessive epistasis.

Btw how do you keep thinkin you dont know bio! your saying everything word for word nearly from the Textbook :eek3:

Reply 1889

ViolinGirl

ibysaiyan

same here I have lost that motivation(push) to do any reading :frown:

argh....

I don't even know fission/fusion yet...arrrrrghh. heeeeelpp me. :frown:

Reply 1890

Sakujo

Sup guys I've come to the conclusion that its going to be a rough 4 weeks. I have to kick it into gear and get my head down.

Reply 1891

uer23

ViolinGirl

Whad'ya mean? :smile:

urrrm, because I see you answering the questions, are they from the specification ? And are planning to cover all of it on this thread before the exams ?

Reply 1892

Falcon91

Sakujo

Sup guys I've come to the conclusion that its going to be a rough 4 weeks. I have to kick it into gear and get my head down.

4 weeks? when the heck are your exams :eek3:

Same here mate...but ive been revising so long now its hard to keep focus right when my exams aer drawing close i.e. all of mine in the next 2 weeks and im scared like never before.

Reply 1893

ViolinGirl

Falcon91

Describe the concept of dominant and recessive epistasis.

Btw how do you keep thinkin you dont know bio! your saying everything word for word nearly from the Textbook :eek3:

I don't know, i just don't feel ready yet, if you get me :s-smilie:

. Lol, textbook wording is falling into my brain now, I've read through most pages many times now, except mod 4, oh gotta go over that!

Dominant and Recessive Epistasis refer to antagnosistic action of genes, whereby one gene locus masks or suppresses the expression at the other gene locus.

Dominant epistasis- this is where the prescence of a dominant allele at the first locus, prevents the expression of alleles at the second locus. THe first locus is epistatic to the second, of which is hypostatic.
Ratios tend to be 12:3:1 or 13:3
Recessive epistatis- this is where the homozygous prescence of a recessive allele at the first locus, prevents the expression of alleles at a second locus.
Ration tend to be: 9:3:4

Desribe the regions of the brain, and their function and link this to the nervous and endocrine system.

Reply 1894

ViolinGirl

uer23

urrrm, because I see you answering the questions, are they from the specification ? And are planning to cover all of it on this thread before the exams ?

Yes, why?

Reply 1895

ibysaiyan

ViolinGirl

I don't even know fission/fusion yet...arrrrrghh. heeeeelpp me. :frown:

Fission is where a heavy radioactive Unstable nuclei breaks into light nuclei (daughter) and with large amount of heat along with it oh also the breaking is initiated by firing neutrons through thermionic emission into the Isotope.
As for fusion ... I cant remember much I need to start revising that too along with binding energy :/
I feel so exhausted with my pc giving off this heat.. + room temp = bad

Reply 1896

ViolinGirl

Falcon, I'll be back later. Gotta do chem now.

Reply 1897

Sakujo

Falcon91

4 weeks? when the heck are your exams :eek3:

Same here mate...but ive been revising so long now its hard to keep focus right when my exams aer drawing close i.e. all of mine in the next 2 weeks and im scared like never before.

Last one is on 29th :sigh:

Reply 1898

ibysaiyan

Sakujo

Last one is on 29th :sigh:

same

Reply 1899

aiden1234

hey everyone, when it comes to commercial applications of plant hormones..how much is everyone learning? because that double spread seems full of stuff we dont really need to know? is it worth learning like one?