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Wednesday, 28 June 2017

Cell division - Mitosis & Meiosis comparison

Mitosis Vs. Meiosis


Points of comparison
Mitosis
Meiosis
Stages
Lasts in 4 stages
Lasts in 8 stages
Separation of chromosomes
Identical chromatids separate as independent chromosomes
Homologous chromosomes ( each with 2 chromatids ) separate
Pairing of chromosomes
No pairing occurs
Pairing occurs to form tetrads
Number of the resulting cells
2 diploid cells (2n each)
4 haploid gametes ( n each)
Occurs in
Somatic cells
Gonads
Crossing over
Does not occur
Occurs
Chiasmata
Does not occur
Observed during Prophase l and Metaphase l
Prophase


Resulting genetic characters
Identical in each cell & as the mother cell
Each gamete has different characters due to crossing over which allows for genetic variation
Karyokinesis
Occur in Interphase
Occur in Interphase l
Cytokinesis
Occur in Telophase
Occur in Telophase l and in Telophase ll
Phases happen
Once
Twice
Prophase
It usually takes a couple of hours, and therefore it is simple
It takes longer time comparing to the one in mitosis up to a day, and therefore it is complicated
Synapsis
Does not occur
Happens in homologous chromosomes during Prophase
Chromosomal arrangement during metaphase
Chromosomes arrange in one row and centromere divides
Chromosomes arrange in 2 rows & centromere does not divide ( Meiosis  I )
Location of occurrence
In plants: growing tips ( apical meristems in shoots and roots) & cambium layer ( meristematic cells) which give rise to xylem and phloem tissues
In animals: all cells except nerve cells
In plants: anthers & ovaries of flowers
In animals: testis & ovaries.
Considered to be       
A building method of the human body especially in the phases of early development (during Zygote stage - Mitosis is so active then it continues to be active after delivery until it becomes regular) replenishing method for worn out tissues or regeneration of new layers such as your skin epidermal layer.
It is also considered as a reproduction method for some organisms ''Asexual reproduction''
Aims for the reduction of the chromosomal number and genetic variation of organisms - it is carried out by higher advanced organisms in life
''Sexual reproduction''
Discovered by
Walther Flemming
Oscar Hertwig ( described by him for the first time) then by Edouard Van Beneden ( described it for the second time)
Diagram







**************The End**************


Notice: All pictures inside this topic doesn't belong to me - copyrights goes to the owner:
http://bio1510.biology.gatech.edu/
http://www.ducksters.com/science/biology/cell_division.php
https://www.pinterest.com/peggleston22/science/
local-brookings.k12.sd.us 

Recent topics
Difference between animal and plant cells 
http://allaboutbiologyworld.blogspot.com/2017/06/difference-between-animal-and-plant.html

Overview of plant cells - part 1 Structure and function
http://allaboutbiologyworld.blogspot.com/2017/06/overview-of-plant-cells-part-1.html

Difference between Eukaryotes and Prokaryotes
http://allaboutbiologyworld.blogspot.com/2017/06/a-comparison-between-prokaryotes-and.html

Tuesday, 27 June 2017

Difference between Animal and Plant cells

Animal cells Vs. Plant cells

Points of comparison
Animal cell
Plant cell
Shape
Irregular due to possessing only cell membrane
Rigid in shape due to cell wall which consist of compounds that give the cell wall its rigidity
Organelles
Has centrioles, and lysosomes
Small vacuoles relative to those found in plant cells
Lack chloroplasts and cell wall
Has chloroplast( organelle containing pigment chlorophyll which gives the plants their green color), cell wall and central large vacuole.
Lack centrioles
Totipotency
Only special types of cells can regenerate or differentiate to specific type of cells '' these cells are stem cells'' (Embryonic stem cells (Pluripotent) & somatic stem cells ( adult stem cells or multipotent stem cells)
Can originate a whole new complete plant from any single cell
Genes
All genes are found in all cells but not all of them are active e.g., Insulin-producing gene is active in the pancreas and inactive in your lung cells
All genes are active since they have the ability to regenerate from one single cells a complete plant ''Totipotency''
Metabolism
Animal cells cannot perform photosynthesis since they lack chloroplasts
Plants have one specific different process in their life cycle that no other organisms has it ''Beside some algae and bacterial strains''
Which is the photosynthesis due to chloroplasts
During mitotic cell division
In Prophase, a centrosome ( has 2 pairs of centrioles) is found near the nucleus. Each centriole moves to one end of the cell forming spindle fibers.
In Telophase, As the nucleus is now completely divided, the cytoplasm start to divide, a constriction appears & continues in the middle of the cell dividing it into 2 cells.
In Prophase, No centrioles are found. Spindle fibers are formed directly from the cytoplasm
In Telophase, No constriction, a middle lamella is formed to separate the formed cells. The middle lamella is in the form of a chain of fine vesicles followed by the precipitation of pectic compounds and then cellulose is followed forming the cell wall separating plant cells.
Nucleus
It is usually in the middle of the cell
It is usually not centered due to the relatively large size of the central vacuole taking up much space.
Starch granules
Absent - excess glucose is usually connected together in chains forming chains of glycogen which are stored in skeletal muscles and liver for later use
Present
Diagram








Recent topics

Overview of plant cells - part 1 structure and function -http://allaboutbiologyworld.blogspot.com/2017/06/overview-of-plant-cells-part-1.html


Difference between Eukaryotes and Prokaryotes http://allaboutbiologyworld.blogspot.com/2017/06/a-comparison-between-prokaryotes-and.html




Animal cells - structure of the organelles and their functions 
http://allaboutbiologyworld.blogspot.com/2017/06/our-cell-1-structure-function-division.html 

Biology gallery #2 - http://allaboutbiologyworld.blogspot.com/2017/06/biology-gallery-2.html 

Overview of plant cells - Part 1 Structure and function (Cell wall and Pits)

Plant cells

Structure and function

Introduction

Plants are endowed with very unique structures and techniques that help them live a different way of life than us, they have their own immune system and way of defenses methodologies, way of taking up their nutrients, the source of their nutrients, different organs that we do not have and much more we are going to explore in this episode and the upcoming ones as well....

So to begin with, the term cell was firstly used by the English Botanist Robert Hooke to determine the individual unit of the honeycomb-like structure in cork under the compound microscope in 1665.
(Read more about his biography at ---> http://www.ucmp.berkeley.edu/history/hooke.html)

Botany is the scientific study of plants ( and many organisms previously thought to be plants). There are various subfields or sub-disciplines of Botany which may be pure or applied Botany.

Pure Botany
Morphology ( study of plant form)
Physiology ( study of the functions of plant organs)
Anatomy ( study of plant structure)
Taxonomy ( is the science that finds, describes, classifies, identifies, and names plants)
Ecology ( interactions with the environment)
Phytogeography ( The study of the geographic distribution of plants. Also called geobotany)
Genetics ( the study of heredity and variation in organisms)

Applied Botany: Study of the relation of plants with man.
Agriculture The science, art, and business of cultivating the soil, producing crops, and raising livestock; farming.
Horticulture The science or art of cultivating fruits (Pomology), vegetables (Olericulture), flowers (floriculture), or ornamental plants.
Agronomy Is the science and technology of producing and using plants for food, fuel, feed, fiber, and reclamation.
Phytopathology ( plant pathology) is the scientific study of plant disease.
Forestry - The art and science of managing forests, tree plantations, and related natural resources.
Plant breeding - The art and science of changing the genetics of plants for the benefits of mankind.

What are plant cells?
Plants are eukaryotic ( true cells meaning they have organelles) multicellular organisms that composed of millions of cells each of which has its own specialized functions.

What makes plant cells differ from animal cells? 
Plant cells have some distinct organelles and structures that aren't found in animal cells. For example,
1)Chloroplasts which are just one type of the various plastids that can be found in a plant cell, Basically, these powerful organelles that are essential for every plant and mainly contributes to the color of the plant which is the green color that everyone sees due to the pigment contained within the chloroplasts' thylakoids the chlorophyll.
Chloroplasts are spherical to oval-shaped structures, double-membraned, green in color due to pigments contained in such as Chlorophyll A and B, etc..
(Pic. source: http://journal.frontiersin.org/article/10.3389/fpls.2013.00114/full)
Chloroplast
Also, it can vary in shape in many species, For example, Zygnema sp. a type of algae in Phylum: Chlorophyta, has a star shaped chloroplast
Zygnema sp.
Cup-shaped chloroplast in Chlamydomonas sp., Phylum: Chlorophyta
Chlamydomonas sp.

Spiral-shaped chloroplast in Spirogyra sp., Phylum: Chlorophyta
Spirogyra sp.
Besides its various types, it also has a major role in plant cells in their life cycles since it performs one of the processes that is ONLY unique amongst plants and some other bacterial cell types which is the Photosynthesis '' Photo = light, synthesis= manufacture or to make something out of'' ****We will have a complete topic about it discussing anything concerned with plastids, chloroplasts, photosynthesis, and Calvin cycle.**** However, We can define photosynthesis briefly in this well-known equation:
6CO2 + 6H2O + Light (energy coming in the form of photons)---> C6H12O6 + 6O2
Photosynthesis
2)Central vacuole, in plant cells the vacuoles are pretty much large in size which also contributes to the shape and rigidity of plant cells due to its large size relatively compared to that of in animal cells which are very small in size and sometimes they lack a vacuole in animal cells, so the central vacuole is large in size irregular in shape to ovale, membrane-bound by a Tonoplast - Functions as enzyme storage and waste removal.
(Pic.,source: http://fig.cox.miami.edu/~cmallery/255/255hist/255methods.htm)

3)Cell wall is what gives a plant its rigid texture, erect structure ( there are exceptions e.g. weak stemmed plants which have some modifications to hold itself erect)and strong structure.
The cell wall is composed of polysaccharide compounds such as mainly cellulose ( Monomeric unit: Beta 1-4, D-glucose units) thousands of them making up the cellulose, hemicellulose, and lignin.
The cell wall is made up of middle lamella, primary wall, and secondary cell wall.
The middle lamella is the first layer formed during cell division, it is shared by adjacent plant cells, consist of pectic compounds and proteins.
Primary wall of the cell wall, made up of cellulose microfibrils embedded in a gel-like matrix of pectic compounds, hemicellulose, and glycoproteins - the primary wall have thinner areas in their structure which are called pit fields, they contain small openings in the wall through which cytoplasmic extensions are known as plasmodesma (singular word., plural is plasmodesmata) by which a very process is carried out through it..... cell-to-cell communication.

Secondary cell wall which is three-layered and by far is the thickest one amongst all cell wall components due to the more cellulose, hemicellulose and lignin content making the plant which developed a secondary cell wall extremely rigid and tough.

In comparison to animal cell, they have relatively small vacuoles, sometimes they lack it, they have centrioles which are used during cell division to form the spindle fibers.

Pits and their types
The pits again are due to the primary walls which form the holes or openings in the plant cells for cell-to-cell communication ''plasmodesmata'', pits have various types and some are subdivided into other types ( simple pits and bordered pits)
(Pic., source: https://sites.ualberta.ca/~hacke/Lenka-profile.html )
Simple and bordered pits
(Pic.,source: http://www.biologydiscussion.com/eukaryotic-cell/cell-wall-of-eukaryotic-cells-structure-and-function/5890)

Note:
If 2 simple pits opposite to each other= simple pit pairs 
   2  bordered pits opposite to each other= bordered pit pairs
   simple pit + bordered pit opposite to each other= half bordered pit pair
   A simple or bordered pit with no complementary pit field in front of it= blind pit

Different types of bordered pits
Side view of a bordered pit structure
Simple pits - showing transportation within the cell
Upper view of bordered pits structure

Half-bordered pit pair
Pit borders are due to the bending or overarching of the secondary wall of the cell wall, semi-enclosed making a mouth like structure which is the Pit aperture through which the communication happens.

My newly released video is about this overview in case anyone finds it easy to learn from videos 
Link - https://youtu.be/t02MT4heQEA

Some other educational videos that might help you which I don't own - copyrights goes to the owners
Khan academy - https://www.youtube.com/watch?v=zdvKhaQxvag (Plant cell walls)
Shomu's Biology - https://www.youtube.com/watch?v=V-Y-FOexHXE ( Plant cell wall structure and function)