Welcome Back I hope you all had a
Welcome Back! I hope you all had a wonderful and relaxing break after your midterm exams – seriously though you deserve it for surviving. Today is the first day of 3 rd Marking Period which means…. We have finally reached our genetics unit! Woo! To prepare for today please: • Grab a vocab packet from the front table • Grab the mitosis vs meiosis diagram off the front table • Get out a notes sheet and something to write with
Meiosis
Meiosis • Meiosis is the process that complex organisms use to produce reproductive cells called gametes – Gametes: sperm (male) and eggs (female) • The gametes produced by this type of cell division have half as many chromosomes as the organism’s somatic cells – If a human somatic cell has 46 total chromosomes how many chromosomes does a human gamete cell have?
Meiosis • Meiosis consists of 2 distinct series of stages that a relatively similar to mitosis – Meiosis I and Meiosis II – Both Meiosis I and Meiosis II have their own set of Prophase, Metaphase, Anaphase and Telophase and Cytokinesis • Just like during mitosis, before meiosis begins, all of the cells DNA must be replicated
Meiosis vs Mitosis • The major difference between Mitosis and Meiosis occurs during Meiosis I. – During Mitosis Metaphase/Anaphase – Every chromosome lines up on the metaphase plate and sister chromatids get separated. – During Meiosis I Metaphase/Anaphase Homologous chromosomes line up side by side along the metaphase plate and homologous chromosomes are separated.
Meiosis vs Mitosis
Meiosis vs Mitosis • Mitosis I turns one 2 n cell into two 2 n cells • Meiosis turns one 2 n cell into four 1 n cells
Meiosis I
Meiosis II
So let’s go through the process together… You will need two different colored writing utensils!
Crash Course Video 1. What are homologous chromosomes? 2. How many chromosomes do human sperm/eggs contain? 3. What two processes occur during Prophase I that allow for greater variation? 4. What specific chromosomes are not able to cross over? 5. What type of cells are produced at the end of meiosis?
New Genetic Combinations • Meiosis is very important to creating new genetic combinations • Meiosis is very much responsible for the diversity in our world • Three processes during meiosis aid in increasing diversity: 1) independent assortment 2) crossing over 3) random fertilization
Independent Assortment • In humans, each gamete receives one chromosome from each of the 23 pairs of homologous chromosomes • Offspring can receive either of all 23 chromosome pairs by chance
Independent Assortment • Independent assortment is the random distribution of homologous chromosomes during meiosis • Each of the 23 pairs of chromosomes separate differently • Because of this, there are over 8 million possible gametes
Independent Assortment
Crossing Over • Crossing over adds even more genetic combinations to increase diversity
Random Fertilization • Each new individual made by joining randomly of 2 gametes • Increases genetic variation
Gamete Formation
Gamete Formation • Meiosis is different in males and females • Males – spermatogenesis • Females - oogenesis
Spermatogenesis • Process by which sperm are produced in male animals • Occur in testes • Starts with 2 n cell which swells to become a germ cell • Germ cell undergoes meiosis I and meiosis II producing four haploid (n) cells • 4 n cells change to become sperm
Spermatogenesis
Oogenesis • • Process by which an ovum is made in females Occurs in the ovaries One 2 n cell swells to become germ cell After meiosis I, cytoplasm divided unequally, one cell gets nearly all, other called a polar body, gets much less
Oogenesis • Now the two cells go through meiosis II, the cytoplasm is divided unequally again • Largest cell becomes the ovum (egg) • End result, one large egg and three small polar bodies
Oogenesis
Sexual Reproduction
Sexual Reproduction • Formation of a new individual by a combination of two haploid sex cells (called gametes). • Fertilization - combination of genetic information from two separate cells that have one half of the original genetic information
Gametes • Gametes for fertilization usually come from separate parents • Female produces an egg • Male produces sperm
Haploid vs Diploid • Gametes are haploid and have a single set of chromosomes. • Cells that are diploid, have two sets of chromosomes
Female Reproductive System • The female reproductive system is designed to carry out several functions. – It produces the female egg cells necessary for reproduction. – The system is designed to transport the ova to the site of fertilization. – The next step for the fertilized egg is to implant into the walls of the uterus, beginning the initial stages of pregnancy. – If fertilization and/or implantation does not take place, the system is designed to menstruate (the monthly shedding of the uterine lining).
Female Reproductive System • In addition, the female reproductive system produces female sex hormones that maintain the reproductive cycle. – Uterus (womb) : The uterus is divided into two parts: the cervix and the corpus. The corpus easily expands to hold a developing baby. – Ovaries: The ovaries produce eggs and hormones. – Fallopian tubes: Connects the ovaries to the uterus. The egg will travel from ovaries to the uterus. Fertilization normally occurs in the fallopian tubes, then the egg will move to the uterus
Male Reproductive System • To produce, maintain, and transport sperm and protective fluid (semen) • To discharge sperm within the female reproductive tract during sex • To produce and secrete male sex hormones responsible for maintaining the male reproductive system
Male Reproductive System • Testicle Responsible for making testosterone and generating sperm. • Penis - Semen is expelled through the end of the penis during reproduction.
WARM UP! Hope you all had an amazing weekend! PATRIOTS WON! • List ALL of the functions of both the ovary and the testicle.
Benefits • Creation of genetically unique organism – Because of random fertilization, independent assortment and crossing over, no two offspring from the same parents will be genetically identical to each other • Allows for more biodiversity!
Disadvantages • Time and energy to find mate • Body energy used to produce gametes
Mating Behavior
Mating Behavior • Mating behaviors are dependent on species. • There are two major types of mating behavior: – Monogramy – Polygamy
Monogamy • When two animals exclusively mate with each other.
Polygamy • When animals have multiple different mating partners – Polygyny – when one male mates with multiple females. – Polyandry – when one female mates with multiple males.
Mating Rituals • Calling – Some animals “sing” to attract mates
Mating Rituals • Displays • Animals can be found “dancing” to be found attractive. The most attractive is the one who will earn mating rights.
Mating Rituals • Nuptial gifts • Other animals will attract a potential mate with a gift.
WARM UP Good morning! I hope you all enjoyed our snow… (in case you can’t tell I’m a little salty) List one advantage and one disadvantage for both Sexual Reproduction and Asexual Reproduction
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