B5 Revision

Growth and Development

An accelerated revision resource

Revision IS important

WARNINGThis PowerPoint is not a substitute for active revision using notes, the workbook and revision guide.

You also need to do plenty of past papers to get exam practice.

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Growing and Changing

• We develop as we grow older• Larger animals and plants are built of specialist cells

arranged in particular ways

You need to be able to name examples in each category for animals and plants

Cells Tissues Organs Systems Organisms

Red blood cells

Nerve cells

Palisade cells

Xylem cells

Phloem cells

Xylem tissues

Muscle tissue

Nervous tissue

Blood

Flower

Biceps muscle

Eye

Leaf

Root

Lungs

Root system

Respiratory

Skeletal

Nervous

Digestive

reproductive

Buttercup

House fly

Human

Cat

Dolphin

Earthworm

Oak tree

Single Cell to Fully Grown

• Human fertilised egg cells are called ZYGOTES

• After 10 days the zygote has 100 cells• After 2 months the major organs have

formed• An adult human has about 1014 cells• In plants, growth is at the tips of roots

and shoots in areas called MERISTEMS. There are also meristems to make the stems thicker and in side buds for when they grow

Growing Back• Plant meristem cells are unspecialised and can

continue to grow throughout the plants lifetime.• Newts have spare unspecialised stem cells to

allow them to grow back damaged or lost parts.• Human stem cells are specialised e.g. for skin.• Plants can be grown by using their meristems

e.g. from cuttings. These are dipped in hormone rooting powder containing AUXINS to aid root growth. The new plants are clones.

Nucleus Revision

• Humans have 46 chromosomes (23 pairs one set from mother one set from father)

• Human sex cells (Gametes) have 23 chromosomes

• Humans have about 30 000 genes• Genes code for PROTEINS• DNA can make an exact copy of itself• Human red blood cells have no nucleus

DNADNA

Mitosis – For growth and repairInterphase

DNA dividesCell growsOrganelles divide

(Prophase)Chromosomes has identical copy attached to itChromosomes become visible

(Metaphase)Chromosomes line up in the equator

(Anaphase)Chromosome copies separateCopies move to opposite ends of the cell

(Telophase)New nuclear membranes formCytoplasm divides2 identical cells produced (also identical to parent cell)

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Don't forget about MEIOSIS

•A type of cell division that produces gametes

• It is important in meiosis that the cells produced only contain half the chromosome number of the parent cell.

•A zygote contains a set of chromosomes from each parent

ZygoteZygote

GametesGametes

MeiosisMeiosis

ZygoteZygote

GametesGametes

Sexual Reproduction

• Involves the fusion of male and female gametes (sex cells)

• From any individual, no two gametes are the same. The chromosomes they have are a mixture of maternal and paternal ones

• Gametes have HALF the number of chromosomes that the rest of the body has

• Gametes are made by MEIOSIS which halves the number of chromosomes.

DNA Structure

• It has a DOUBLE HELIX structure

• There are 4 bases that always pair up in the same way (base pairing)

• Adenosine (A) with Thymine (T)• Guanine (G) with Cytosine (C)• It can make an exact copy of

itself– Weak bonds between the bases

split– A new strand starts to form on

the free bases

Making Proteins

• Proteins are made up of amino acids• There are about 20 possible amino acids to

use• 3 bases on the DNA code for a single amino

acid (triplet code)• mRNA forms on the untwisted DNA • mRNA has Uracil (U) instead of thymine (T)• mRNA moves out of the nucleus through pores• Ribosomes attach to one end of the mRNA and

as they move along amino acids are added to make up the protein

Specialised Proteins

• We have around 300 different specialised cells• Genes are lengths of DNA and they make proteins

Antibodies

Protein Found in Property

KeratinStrong and insoluble

Elastin Skin Springy

Nails, hair skin

Tough but not very stretchy

SkinCollagen

Enzymes All cells, the gut Speed up chemical reactions

Antibodies In the blood Defend against disease

Gene Switching

• The one-gene-one-protein theory• 25 000 – 30 000 genes in humans • In stem cells all these genes are

switched on• As some cells specialise some are

switched off

Stem Cells

• Stem cells produced could be used to treat heart disease, diabetes, Parkinson’s and lots more

Phototropism

• Plant stems will grow towards the light. This is PHOTOTROPISM

Plants growing towards the light

Plants grown in normal light. Green and sturdy

Plants grown in the dark. They are CHLOROTIC (yellow) and spindly (ETIOLATED

Auxins at Work

• More auxin goes to the dark side

• Auxin makes the cells grow faster

LIGHTLIGHT

• Conclusion– Auxin is produced

by the tip of the oat seedling

LIGH

TLIG

HT

LIGHTLIGHT

Questions

• What happens in the normal cell cycle?

• What happens during cell growth?What happens during cell growth?

• What happens during Mitosis?What happens during Mitosis?

–Cell growthCell growth–MitosisMitosis

–Number of organelles increaseNumber of organelles increase–Chromosomes are copied by separating DNA Chromosomes are copied by separating DNA strands and forming new strandsstrands and forming new strands

–Copies of the chromosomes separateCopies of the chromosomes separate–The cell dividesThe cell divides

More questions

• In which organs do cells divide by Meiosis?

• How many chromosomes are in the gamete How many chromosomes are in the gamete if the parent cell has 46?if the parent cell has 46?

• How many chromosomes does the zygote How many chromosomes does the zygote have? Where are they from?have? Where are they from?

– Ovaries and TestesOvaries and Testes

– 2323

– 4646– A set from each gamete. (from each parent)A set from each gamete. (from each parent)

Questions

• Where is the genetic code found?•

Where are proteins made in cells?Where are proteins made in cells?

How does the code get into the cytoplasm?How does the code get into the cytoplasm?

How many different bases are in DNA?How many different bases are in DNA?

How is the order of the amino acids in proteins determined?How is the order of the amino acids in proteins determined?

In the cytoplasmIn the cytoplasm

In the nucleus of every cellIn the nucleus of every cell

A copy of the gene carries the code (RNA)A copy of the gene carries the code (RNA)

Four different bases, always pairing the same wayFour different bases, always pairing the same way

The order of bases in a gene is the codeThe order of bases in a gene is the code

Cut stemsCut stems from a plant can from a plant can develop _______ develop _______ in the presence of in the presence of plant hormones (________) and grow into a complete plant plant hormones (________) and grow into a complete plant which is a _______ of the parentwhich is a _______ of the parent

rootsrootsauxinsauxins

cloneclone

Plant HormonesPlant Hormones

Phototropism is _________________________. It Phototropism is _________________________. It increases the plant’s chance of _________.increases the plant’s chance of _________.

Light causes ______ to move to the opposite side of the Light causes ______ to move to the opposite side of the shoot tip. The cells on the side with more auxin grow shoot tip. The cells on the side with more auxin grow ______. ______.

PhototropismPhototropismthe plant’s response to lightthe plant’s response to light

survivalsurvival

auxinauxin

biggerbigger

Questions

• Division of a cell by mitosis creates ____ cells.• When do mammalian embryonic cells become

specialised?

• How do cells control which proteins they produce?

• If animal stem cells can produce cells to replace damaged tissues, what can plant stem cells do?

They can inactivate genes or reactivate inactivated genes.They can inactivate genes or reactivate inactivated genes.

Develop into any type of plant cellDevelop into any type of plant cell

twotwo

The eight cell stageThe eight cell stage