reading quiz why sexual reproduction? –mixes 2 organisms traits to increase the likelihood of...

Reading quiz• WHY sexual reproduction?

– Mixes 2 organisms traits to increase the likelihood of passing the BEST traits & increasing survival of that species.

– NOT a guarantee that these BEST traits will all show up in 1 offspring. It’s RANDOM chance. HOPE to get the best.

• DOES NOT CAUSE EVOLUTION– Evolution is driven by many things and

MUTATIONS is one of them.– Cloning (mitosis) CAN have mutations too! Sexual

Repo (Meiosis) speeds up passing mutations around which speeds up the slow process of Evolution.

• Tell me when there is 3 minutes left so I can pass back the quiz.

• See me after school for questions (room 602- 3:00 to 3:30)

Web quest review!

Meiosis!These notes will be done quickly. They are review of your reading & web quest. Now is the time to ask questions. I will post these

notes on the hw web so pay attention & ask questions

More information on your good friends… Chromosomes!

I.) In cells, chromosomes exist in pairs. One from mother and one from its father.

A.) In humans, we have a total of 46 chromosomes. 23 chromosomes from mom and 23 chromosomes from our dad.

1.) Therefore, we have 23 pairs of chromosomes.

2.) These pairs of chromosomes are called HOMOLOGOUS pairs.

a.) Same in SIZE and FUNCTION.

b.) They have genes for the same TRAITS in the same order.

3.) Any cell with 2 sets of chromosomes (1 complete set from mom and 1 from dad) is called a DIPLOID cell.

a.) ALL the cells in your body are diploid EXCEPT the GAMETES (sex cells).

b) Gametes only have one set of chromosomes which means they only have 23 chromosomes SO we call them HAPLOID

c. )WHY? If the chromosome # wasn’t halved then each generation the chromosome number would double.

Meiosis

I.) Specialized cells in reproductive organs (OVARIES in females and TESTES in males) undergo a form of cell division called meiosis to produce haploid gametes.

Sperm/Egg• You pass on half

your genes to offspring

• You must make a gamete (sperm or egg cell) with half of your chromosomes

• Each gamete randomly receives 1 of the 2 versions of each chromosome

Meiosis

• Each parent cell produces 4 haploid daughter cells

• Each daughter cell has 1 set of chromosomes (instead of the usual 2) OR (half of the parent’s chromosomes)

# of Possible Gametes

• There are 223 possible chromosome combinations to make a gamete

• =8,388,608 possibilities

• So you are 1 out of 8,388,6082 possibilities

• You are quite literally 1 in a trillion (1 of 70,368,744,200,000 possible combinations of your parents)

Which side of the cell the chromosome lines up on = 223 + crossing over!!!

What’s the Point?

• Meiosis allows us to have offspring that are different and have a unique combination of genes

• This increases diversity in the population

• Increased diversity means increased ability for the species to survive and adapt to new situations

• HW compare Mitosis & Meiosis.

• Use your brain & the worksheet to answer as much as possible.

• Consult your notes/Internet if necessary, just not other biology students.