cells become specialised into different types of cells
meristems
where you find stem cells in plants
tissue
group of cells
organs
group of tissue
systems
group of organs
some specialised animal cells
erythrocytes - carry oxygen from the lungs to respiring animals
neutrophils - ingest invading pathogens
stem cells are unspecialised cells that have the potential to differentiate into different specialised cells
totipotent
stem cells which can divide and differentiate to form a whole new organism eg newly fertilised egg (zygote) and the first 8-16 cells from the first few mitotic division
pluripotent
can become any type of tissue but not a whole organism eg embryo larger than 100 cells
multipotent
can form a range of cells but not all different types of cells within a tissue eg stem cells in bone marrow can form different blood cells
unipotent
can only form one type of cell (skin cells)
3 uses of stem cells
replace organs and cells
developing new pancreatic tissues
new drugs
sperm
many mitochondria carry out aerobic respiration
ATP provides energy for the tail to move and propel towards the ovum
enzymes are released from the acrosome, enzymes digest the outer protective layer covering the ovum, allowing the sperm to enter the ovum
epithelial cells
is lining tissue
squamous epithelial cells are flattened in shape
many of the cells have epithelium have cilia
palisade cells
within leaves are adapted for photosynthesis because they are long and cylindrical
large vacuole so that chloroplasts are positioned nearer to the periphery of the cell
many chloroplast
guard cells
lower epidermis, do not contain chloroplast
more flexible and more rigid
gaseous exchange can occur
root hair cell
hair like projection greatly increases surface area for absorption of water and mineral ions
have special carrier protein in the plasma membrane in order to actively transport the mineral ions in
connective tissue
these hold structure together and provide support eg bone, cartilage
muscle tissue
made out of cells that are specialised to contract and cause movement
nervous tissue
made of cells specialised to conduct electrical impulses
vascular tissue
xylem and phloem
cartilage
hyaline cartilage - forms the embryonic skeleton , covers the end of long bones in adults, joins rib to the sternum and also found in the nose
fibrous cartilage - occurs in disc between vertebrae in backbone