Sex determination systems

What do tiny insects like aphids and some sharks have in common? Read on to find out.

Do you know that not all organisms are like humans having the XY sex determination system?

Human males are XY and females are XX. (humans beings)
The female has two large sex chromosomes and the male has one large and one small sex chromosome.

The other systems are:

(1) XX female and XO males (grasshopper, cockroaches and crickets)
The females have two sex chromosome and the male has only one sex chromosome.

(2) ZZ male and ZW females (most birds and some insects)
The males are the ones who have two large sex chromosomes and the female has one large and one small sex chromosomes ie the reverse of that of human beings.

(3) Diploid females and haploid males (honey bees and ants)
The fertilised eggs become females (queens and worker bees) and the un-fertilised becomes the drones or kings.
(4) Temperature during incubation of eggs controls sex of offspring(crocodiles, turtles and tortoises)

(5) Sex changes with the environment. The dominant fish may change from one sex to the other depending on the population requirements at the time. (clown fish and many other fish)
(6) Hermaphrodites (nematodes, snails, slugs and earthworms)
They are both male and female at the same time as they have both fully functional male and female sex organs.

(7) Parthenogenesis (many species of insects, especially aphids)
The females give rise to offspring without sex. the eggs develop into new babies without the need for fertilisation. This is also known as virgin birth. It has also been documented in lonely female sharks kept in labs from birth with no other sharks in sight for miles around.


You may want to click on the following link to read more on this topic. Sex determination systems

Please do understand that these are all normal sex determination systems in these particular organisms. Do not mix these up with sex aberrations which are actually mistakes in chromosome or chromosomal mutations.


Cheers

We will discuss the sex aberrations in man on another posting as you have requested many times in class.

Panda galore

Read more about the panda-monium at Wolong National Nature Reserve, in Sichuan Province, south west China

All hese 16 pandas were bred at the breeding centre in southern China. They are extremely rare even in China where they are endemic. They are also difficult to bred as they are very slow breeders who give birth to only one or at most 2 cubs per pregnancy. Their diet is also very restrictive, feeding only on bamboo leaves and shoots.

Cheers

Petroleum from wood-chips and sunlight?

Hi,


Making petroleum from wood-chips and other plant wastes is feasible now.

Clink on this link to access Sundrop Fuels looks to combine sunlight + wood-chip to make gasoline

Not only is it carbon neutral to use this petroleum, it is very cheap too. It costs only US$2 per gallon compared to US$60 to $80 per gallon for the conventional fossil fuel petroleum.

Since wood-chip, corn, wheat and rice stalks and leaves are produced in large quantities in crop production, these wastes can be turned into cheap petroleum. The energy for the chemical conversion comes from the unlimited sunlight. Light energy is captured by a series of mirrors and directed onto the plant wastes. The high temperature of 1,200 1,300 degrees Celsius created would break the chemical bonds in the organic material and make new bonds to turn them into fuel.


Cheers

Sea slug that could do photosynthesis?

Hi,

Look at this marine slug, a shell-less snail. It is green as it has chloroplasts. It can make its own food by photosynthesis.

Read how this organism has accomplished this marvelous feat. Click on the link below to find out more about it. Green sea slug is part animal, part plant.

Scientists led by Dr Sidney Pierce found that this slug contained chloroplasts containing chlorophyll taken from an algae by the name of Vancheira. Once the slug has enough chloroplasts under its skin, it does not have to eat for the rest of its life. Just like a plant does not eat food.

Why cannot we also have chlorplasts so that we do not have to eat, but just absorb energy for all our needs from the sun like greeen plants?

Bizarre.

Cheers

No more heavy metal poisoning from farmed fish

Man changed sociologically and culturally when he stopped being a hunter-gatherer.He settled down to crop growing and domesticating animals for food, milk, eggs, pelt and for transport.

Here comes the next revolution. Instead of hunting the seas for marine fish for food, farming marine fish on land. It is profitable, gives fresher produce, more predictable quality and quantity.

Scientists have done fresh water fish and prawn farming for a long time. However, the produce tends to be affected by the pollution of the fresh waters. Mercury and other heavy metal poisoning is a perennial problem associated with this kind of farming.

Read the article by clicking on the link UNCW aquaculture facility explores salt-water fish farming to know more about it. Scientists are involved from the beginning as they have to develop and provide new strains of marine fish that are amenable to farming on land!



Cheers

Lesson on digestion of food

Hi,







I hope the 3 videos have helped you to understand:

-peristalsis, the wave-like rhythmic movement in the stomach and intestines to churn food and move food along the gut.

-mechanical digestion or chewing in the mouth. teeth break food into smaller particles

-chemical digestion or breaking down of food into smaller molecules so that they can be absorbed into the blood stream.

-producctionof of enzymes in mouth, amylase digests starch into maltose.

-production of enzyme pepsin and hydrochloric acid in the stomach. these help in the breakdown of proteins and kill germs in the food respectively.

-production of lipase and digestion of fats in the small intestine.

-villi in the small intestine to increase surface area in contact with digested food so that absorption is more efficient.

-absorption of digested food, small diffusible molecules into the blood stream.

-the circulatory system carries the food in the blood to all parts of the body for use or assimilation.

Cheers

Lesson on Osmosis and diffusion

Hi,
Happy New Year to all my students.
There are a number of videos in this lesson. I think you would enjoy all of them. Some show experimental results and others show cells under the microscope as they undergo changes in solutions of different concentrations.









This set of 5 videos are very thorough. Parts 1 and 2 are simpler. Parts 3, 4 and 5 would be very relevant to the pure biology students.












Cheers