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Biology Notes- Evolution of Australia Biota

- Distinguish between the processes if meiosis and mitosis in terms

of the daughter cells produced.

Meiosis MitosisDenition A type of cellular

reproduction in where the

numbers of

chromosomes are

reduced by half by the

separation of

homologous

chromosomes, producing

haploid cells!

A type of ase"ual

reproduction in where the

cells are divided into #

producing replicas with

the same number of

chromosomes in each

diploid cells

$ype of %eproduction &e"ual Ase"ual

'here does it occur( )umans, animals, plants, fungiAll organisms'hen cells are separated Di*erent +denticalrossing over es, mi"ing of chromosomesNo.unction /enetic diversity, se"ual

reproduction!

ellular reproduction for

growth and repair!Number of daughter cells haploid cells # diploid cellsNo! of Division # 0hromosome Number %educed by half &ame

reates &e" cells for female egg

cells or male sperm cells

Ma1es everything other than se"

cells

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Mitosis

Interphase

- +nitialising cell division- ells prepare to divide 7 genetic materials double

Prophase

- 8airing of chromosomes- hromosomes thic1en and shorten! entrioles move to the opposite sides

of nucleus! Nucleus disappears and nuclear membrane disintegrates!

Metaphase

- Meeting of chromosomes in the middle- hromosomes arrange in the middle of cell, become attached to spindle

bres by centromeres! )omologous chromosomes do not associate!

Anaphase

- hromosomes are pulled apart- &pindle bres contract pulling chromatids to the opposite poles of the cell!

Telophase

- $wo cells- hromosomes uncoil! &pindle bres disintegrate! entrioles replicate!

Nuclear membrane forms! ells divide!

$he division of the cytoplasm 9yto1inesis: after mitosis is necessary to

ensure the cells have the correct number of chromosomes! Mitosis doubles

the numbers of chromosomes in a single cell so the cell divides in two to

preserve the chromosome number 9#n:!

Meiosis

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Prophase- hromosomes separate into homologous pairs- Nuclear membrane brea1s down- rossing over occurs- hromosomes split into chromatids

Metaphase 1- hromosomes align in pairs towards the middle of

cell- hromosomes attached by centromere- &pindle forms at centre of cell ma1ing the

chromosomes pull away

Anaphase 1- hromosomes pairs separate, moves to opposite

end of cell

Telophase 1- # Daughter cells form- hromosome number halved

Cytoinesis 1- Daughter cells not identical, have half of the

original number of chromosomes

Metaphase !- hromosomes align at the centre- &pindle forms on the poles of the cell, pulling away

the chromatids

Anaphase !- hromatids move apart, to opposite poles

Cytoinesis !- daughter cells, not identical to each other, have

half the original chromosome number

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Meiosis produces "ametes. "ametes are se" calls andhave half the normal number of chromosomes! Mitosis isthe process where the cell nucleus divides into #!+n multicellular organisms mitosis occurs in the body cells#somatic cells: for growth, repair and maintenance whilemeiosis occurs in the "onads #testes and o$aries% forse"ual reproduction!

&umans ha$e '( chromosomes nown as thediploid number #!n)'(* !+ pairs of chromosomes%.

,ach haploid cell produced by meiosis has !+chromosomes.

ariation in Meiosis- Crossing o$er occurs where the arms of

homologous chromosomes e"change geneticmaterial!

- $his occurs in the rst stage of meiosis- +n this process the ad;acent chromatids twist, split, and ;oin up with di*erent pieces!- New combinations are made, by lin1ed genes separated!- 5ariation is produced in se"ual reproduction

- Meiosis produced into haploid cells which show variation produced randomsegregation of the chromosomes pairs when crossing over!

- Due to all the variations between individual gametes, there are many potential

combinations that can occur to form a uent reproduction =ess fre>uent reproduction

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0imilarities

Both male and female gametes re>uired for fertilisation

/ametes are provided with a watery environment where fertilisation will occur!

All possible fertilisations will grow to form uatic environment, allowing the gametes and young producedafter fertilisation to spread and live in large bodies of water!

Internal ertilisation- 6ccurs inside the body of the female in animalsfemale part of the plants!- .urther development of the new organism still needs water!

- Direct transfer greatly increases the chance of successful fertilisation!- $his is done by se"ual intercourse 9copulation:

- +n Cowering plants the male gamete is the pollen and once the pollen lands onthe stigma in the female part of the plant* the pollen goes down the ovary andthe male gamete is transferred and the ovum is fertilised!

- Male reproduction organ is called the stamen, with # parts the anther and thelament!

- Meiosis occurs inside the anther, resulting in the formation of haploid pollen grains!onsists of # haploid nuclei!

- .emale reproductive organ is called a pistil.onsisting of 0 or more Carpels found

at the centre of the Cower! +t consists of the 0tigma* style and o$ary! +nside the

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ovary are ovules and this is where meiosis occurs resulting in the formation of haploid cells, one is the o$um #egg%.

Di/erence between seual and aseualreproduction #and conditions under which aseual reproduction is anad$antage%.

# or more 0 or more

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Ase"ualreproduction

&e"ualreproduction

N

umberoforga

nisms

0

parentneeded

#

parentstomate

elldivisio

n

ellsdividebymitosis

,budding,ssion,orregeneration

ellsdividebyMeios

is

$ime

5eryshortperiodoftime

&everalmonths

/ame

tesarenotproduced

/am

etesproducedbyth

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Number ofo*spring

Advantage No mate needed!Many o*spring

produced >uic1ly!$ime eFcient! =essenergy!0tableen$ironments $erylittle change.

/enetic variationin the o*spring!

6rganism isprotected! 2ni>ue!reates anevolution!

Disadvantage

No variation in theo*spring! /eneticdisease, o*spring willhave too!+f change happens, it

is hard for them tosurvive!

%e>uires bothse"es toparticipate! Moreenergy

E"amples &pider plants,bacteria, yeast,

;ellysh

Mammal, sh,reptiles, birds,insects

- Discuss the relati$e success of these forms of fertilisation in relation tothe colonisation of terrestrial and a2uatic organisms

- 6rganisms in a>uatic environments are successful in reproduction and survival asthey have adaptions suited to reproducing in this type of environment!

- $his means they have to completely rely on their environment in providing its waterfor fertilisation!

- 'ater protects the gametes from drying or heat stressed- dead!

- )owever, in order to survive on land, organisms needed to overcome thedependence on a>uatic environments for fertilisation by providing their

own enclosed moist environment within the female reproductive territory,protected from the dry terrestrial environment!

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,ternal ertilisation

+n an a>uatic environment

- 6rganisms attempting to carry out e"ternal fertilisation in a>uaticenvironments are highly successful!

- /ametes do not dry out or dehydrate and they are able to survive inwater!

- But at the same time they must produce large amounts of gametes tocompensate from other factors such as predators, disease, and dispersalto unsuitable environments 9temperature, currents:!

+n a terrestrial environment 9land:

- 6rganisms attempting to carry out e"ternal fertilisation on land are notsuccessful at all due to the reliance upon a water environment forfertilisation and to transfer the gametes before they dry out!

Internal ertilisation

+n an a>uatic environment

- +nternal fertilisation is not necessary adaptation for most a>uatic speciesas there is already water for fertilisation!

- )owever it is successful in this environment!- .ewer gametes are re>uired because of the higher chance of the gametes

uniting!

+n a terrestrial environment

- +nternal fertilisation has only been possible on land because it does notneed water environment for fertilisation as they already is a moistenvironment for the transfer of gametes!

- 5ery successful as it is the mechanism for direct transfer of gametes whichavoids factors such as dehydration of gametes and loss by dispersal,therefore fewer gametes are re>uired!

- Environment is enclosed in a conned space, protecting from predationand disease!

- Describe some mechanisms found in Australian