REPRODUCTION AND DEVELOPMENT OF FLOWERING PLANTS (ANGIOSPERMS)

Flowering plants have sporophyte and gametophyte stages. The sporophyte is diploid and consists of roots, stems, and leaves. The sporophyte produces flowers for sexual reproduction. Flowers produce haploid spores that develop into gametophytes. The female gametophyte is embeddcd in floral tissues. The male is released as pollen grains.

Accessory structures form the non reproductive parts of the flower.

A flower has a ring of leaf like sections round the base.
These are called SEPALS.
Inside the SEPALS are the PETALS.
The PETALS can be a variety of shapes and colours.
The PETALS form the COROLLA.
The SEPALS form the CALYX

Reproductive parts include the stamens (male) and carpels (female).

1) THE STAMEN
Inside the COROLLA are slender stalks.
These are called FILAMENTS.
At the end of the FILAMENT is the ANTHER.
The ANTHER and the FILAMENT together form the STAMEN.
The STAMEN is the MALE reproductive ORGAN.
Pollen grains are found on the ANTHER.
2) CARPEL
At the centre of the COROLLA is the CARPEL.
This is the FEMALE reproductive ORGAN. It is made up of the:
1)STIGMA

2)STYLE

3)OVARY.
The pollen from the male part, the STAMEN, is needed to fertilise the female part, the CARPEL.
The female reproductive organ is the CARPEL
The male reproductive organ is the STAMEN

Pollen is basically sperm packed inside a nutritious package. When it first evolved it was transferred by wind currents. Later it was transferred by insects. Most species of angiosperms have coevolved with pollinators attracted to their pollen and nectar. Coevolution refers to two (or more) species jointly evolving as an outcome of close ecological interactions. Plants with flowers that attracted insect pollinators had a reproductive advantage. Plant structures that were more attractive to pollen-delivering insects were favored. The more attractive plants proved to be good sources of food for the insects.
In the ovary, eggs develop, fertilization occurs, and seeds mature.

SO LET'S HAVE A LOOK AT WHAT MAKES UP THE OVARY
The OVARY contains one or more OVULES.
The OVULES are the parts that develop into seeds. They contain female egg cells.

Double fertilization is a distinctive feature of angiosperms. The male gametocyte delivers two sperm to an ovule. One sperm fertilizes the egg and the other fertilizes a cell that gives rise to endosperm that supports the embryo.Pollination is the transfer of pollen grains to the surface of a receptive stigma. Wind, insects, birds, or other agents are often required for the transfer. After a pollen grain lands on a stigma, it germinates and a pollen tube forms, creating a path that the two sperm nuclei will follow to the ovule.
Guided by chemical cues, the pollen tube grows through the tissues of the ovary to an ovule. It carries two sperm nuclei. When the pollen tube reaches an ovule, it penetrates the embryo sac and deposits two sperm. The two sperm are released to accomplish double fertilization.
One sperm fuses with (fertilizes) the egg nucleus to form a diploid zygote. The other sperm nucleus fuses with the two endosperm nuclei to yield a triploid "primary endosperm cell," (endosperm mother cell) that will nourish the young sporophyte seedling.
Endosperm formation occurs only in angiosperms. The fusion of a sperm nucleus with the two nuclei of the endosperm mother cell produces a triploid (3n) cell. This cell will give rise to the endosperm, the nutritive tissue of the seed.

CELLULAR RESPIRATION

PHOTOGALLERY OF CELLULAR RESPIRATION

CELLULAR RESPIRATION

Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. Carbohydrates, fats, and proteins can all be used as fuels in cellular respiration, but glucose is most commonly used as an example to examine the reactions and pathways involved.

GLYCOLYSIS

This process occurs in the cytoplasm irrsepective of the presence or absence of oxygen.In glycolysis, the 6-carbon sugar, glucose, is broken down into two molecules of a 3-carbon molecule called pyruvate. This change is accompanied by a net gain of 2 ATP molecules and 2 NADH molecules.

KREB CYCLE

The Krebs cycle occurs in the mitochondrial matrix and generates a pool of chemical energy (ATP, NADH, and FADH2) from the oxidation of pyruvate, the end product of glycolysis.Pyruvate is transported into the mitochondria and loses carbon dioxide to form acetyl-CoA, a 2-carbon molecule. When acetyl-CoA is oxidized to carbon dioxide in the Krebs cycle, chemical energy is released and captured in the form of NADH, FADH2, and ATP.


OXIDATIVE PHOSPHORYLATION VIA THE ELECTRON TRANSPORT CHAIN

The electron transport chain allows the release of the large amount of chemical energy stored in reduced NAD+ (NADH) and reduced FAD (FADH2). The energy released is captured in the form of ATP (3 ATP per NADH and 2 ATP per FADH2).
NADH + H+ + 3 ADP + 3 Pi + 1/2 O2 ---> NAD+ + H2O + 3 ATP
FADH2 + 2 ADP + 2 Pi + 1/2 O2 ---> FAD+ + H2O + 2 ATP
The electron transport chain (ETC) consists of a series of molecules, mostly proteins, embedded in the inner mitochondrial membrane.


HOW RESPIRATION MAKES ENERGY

Respiration is the release of energy from glucose or other organic substances. Energy is required for growth, repair, movement and other metabolic activities.


There are two main types of respiration -

1) Aerobic respiration

2) Anaerobic respiration


AEROBIC RESPIRATION

It takes place in the presence of oxygen.Glucose molecules react with oxygen molecules to form carbon dioxide and water molecules, with energy being released by the breaking of bonds in the glucose molecules.The energy released from glucose in respiration is used to produce a chemical called adenosine triphosphate (ATP). ATP is where the energy released during respiration is stored for future use.
Glucose + Oxygen ---> Carbon Dioxide + Water + Energy
A lot of energy is released in aerobic respiration - 2900 kj from one glucose and 6 oxygen molecules.


ANAEROBIC RESPIRATION

It occurs when oxygen is not available. In anaerobic respiration the glucose is only partially broken down, and lactic acid is produced - together with a much smaller amount of energy.

Glucose ---> lactic acid + carbon dioxide + energy
This extra oxygen needed to neutralise the harmful effects of anaerobic respiration is called an oxygen debt. In order to get the extra oxygen to 'pay back' the debt, the body continues to breathe deeply for some time after vigorous activity has ceased. When all the lactic acid in the muscles is broken down the oxygen debt has been repaid and normal aerobic respiration resumes.


One measure of a person's fitness is how quickly their breathing and pulse return to normal after exercise. This is because in a fit person aerobic respiration is more efficient, so they build up less of an oxygen debt while exercising, and need less extra oxygen to breakdown any lactic acid in their muscles resulting from anaerobic respiration.
When anaerobic respiration occurs in yeast it is called fermentation. In this case ethanol (alcohol) is produced instead of lactic acid, and this reaction is used in the brewing of alcoholic drinks.
Glucose ---> ethanol + carbon dioxide + energy
All cells are able to synthesize ATP via the process of glycolysis. In many cells, if oxygen is not present, pyruvate is metabolized in a process called fermentation.Fermentation complements glycolysis and makes it possible for ATP to be continually produced in the absence of oxygen. By oxidizing the NADH produced in glycolysis, fermentation regenerates NAD+, which can take part in glycolysis once again to produce more ATP.


During vigorous exercise the body needs a lot more energy. It gets this by breathing in deeper and faster and rushing the oxygen to the muscles in dilated blood vessels. This extra oxygen is then used to release more energy, needed to meet the higher level of demand. Soon a point is reached when the body cannot breathe any faster or harder, and aerobic respiration alone cannot meet the enhanced energy demands. So how do muscle cells get the extra energy they need? They get it by respiring anaerobically.


But anaerobic respiration produces lactic acid, which accumulates in the muscles and causes muscle fatigue and cramps. To avoid damage to cells, lactic acid has to be broken down to carbon dioxide and water immediately the exercise has finished. This is an oxidisation reaction, and requires oxygen.

This extra oxygen needed to neutralise the harmful effects of anaerobic respiration is called an oxygen debt. In order to get the extra oxygen to 'pay back' the debt, the body continues to breathe deeply for some time after vigorous activity has ceased. When all the lactic acid in the muscles is broken down the oxygen debt has been repaid and normal aerobic respiration resumes.

One measure of a person's fitness is how quickly their breathing and pulse return to normal after exercise. This is because in a fit person aerobic respiration is more efficient, so they build up less of an oxygen debt while exercising, and need less extra oxygen to breakdown any lactic acid in their muscles resulting from anaerobic respiration.