REPRODUCTION 1
THE PROCESS OF LIVING THINGS CREATING OFFSPRING. Offspring are the next generation. It happens on multiple levels for multicellular organisms 2
SPECIES SURVIVAL Think back to 7th grade Organisms must produce offspring for the survival of the species (BABIES!) Often, this is a form of sexual reproduction, in some species, like some plants, it is a form of asexual reproduction 3
ORGANISM SURVIVAL Think back to 7th grade On a smaller scale, multicellular organisms must generate new cells for growth, development, and general health and wellness. 4
THERE ARE 2 TYPES OF REPRODUCTION: Sexual and Asexual Reproduction the difference being where the genetic information comes from 5
Sexual reproduction Asexual reproduction Genetic information from 2 sources Genetic information from one source Creates diversity Direct/identical copies Internal and External (Meiosis) Mitosis 6
LET'S START ON THE CELLULAR LEVEL 7
HUMAN BODY HAS 2 TYPES OF SOMATIC CELLS AKA body cells CELLS GAMETES Aka sex cells. Everything in your body, except for the gametes. In a human, 46 chromosomes Sperm and egg. In a human, 23 chromosomes 8
SOMATIC CELLS Made by mitosis Have 46 chromosomes Make up the entire body (except for gametes) Begins at conception and continues for entire life. 9
GAMETES Divide in a two step process, ending with meiosis Have 23 chromosomes; that means they have 1/2 of an organisms entire genome (aka one gene for every trait) Made in the gonads (ovaries and testes) Eggs are made before birth. Sperm begin being made at puberty, and essentially for the rest of a man's life. 10
THE PURPOSE OF MITOSIS IS TO MAKE A DAUGHTER CELL IDENTICAL TO THE MOTHER CELL. In a human we create a copy with the exact (hopefully) number of chromosomes, information. (46 chromosomes) 11
CHROMOSOMES Cell part that determines traits. Found in the nucleus Made of smaller pieces! Chromosomes are made of DNA, small sections of DNA that control traits are called genes 12
CHROMOSOMES 13
MITOSIS 14
1 - INTERPHASE Chromosomes copied (# doubles) human is 92 Chromosomes appear as thread-like coils. Each chromosome and its copy (sister chromosome) change to sister chromatids at the end of this phase 15
2 - PROPHASE Mitosis begins (dividing of cell) Centrioles appear and begin to move to opposite ends of cell Spindle fibers form between the poles (centrioles) 16
3 - METAPHASE Chromatids attach to the spindle fibers Line up across the middle of the cell Think about getting ready to "choose teams" 17
4 - ANAPHASE Chromatids separate and begin to move to opposite ends of the cell This is the choosing of teams! 18
5 - TELOPHASE Two nuclei form Chromosomes appear as chromatin (threads rather than rods) Mitosis ends 19
6 - CYTOKINESIS Cell membrane moves inward to create two daughter cells, each with its own nucleus with identical chromosomes In a human each has 46 chromosomes again. 20
SUMMARY: Creates a copy of the entire genome. "Copies the genome of a mother cell to create an identical daughter cell." There are 5 steps, or phases. 21
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PURPOSE OF MEIOSIS 24
In sexually reproducing organisms, genetic information from two parents must be combined. If meiosis does not happen the number of chromosomes in each generation will double. Remember, it is the number of chromosomes that determines what type of organism you are. Meiosis cuts the genetic information in half, allowing one gene for each trait to be passed on to the next generation. 25
MEIOSIS This cuts the genome in half, creating sex cells each with one gene for every single trait. It starts with meiosis I which is essentially mitosis, then in meiosis II the genome is split. 26
LO O K CL O SE R 27
IMPORTANT DIFFERENCE: there is NO copy made MEIOSIS II Therefore the process cuts the genome in half. 28
Homologous chromosomes: approximately same size, centromere position, and staining patterns. They code for the same traits, and Genes are in similar positions Haploid vs Diploid Diploid are 2n. They have two complete sets of chromosomes. Haploid are n. they have only one complete set of chromosomes 29
MALE AND FEMALE REPRODUCTIVE SYSTEMS 30
MALE REPRODUCTIVE SYSTEM Responsible to make male reproductive cells, sperm. Sperm are made in the testes; which means meiosis takes place here. The production of sperm is controlled by hormones. The hormone associated with the male system is testosterone. 31
FEMALE REPRODUCTIVE SYSTEM Responsible for making female reproductive cells, eggs. Eggs are made in the ovaries; which means meiosis takes place here. It happens in two phases, meiosis I takes place in-utero, and meiosis II takes place later. Hormones control the development and release of eggs once females reach puberty. The hormones are progesterone and estrogen. 32
THE HORMONES Testosterone and estrogen are often associated with specific genders, male/female respectively. They are responsible for the "secondary sex characteristics." AKA the traits we associate with each gender. Males: body hair, muscle mass, deep voices Females: breasts, fat deposits (unfortunately), widening of the pelvis 33
EVELOPMENT 34
REPRODUCTION: Humans reproduce sexually, therefore the sperm and the egg need to combine in order to form a zygote (single cell that undergoes mitotic cell division to eventually become a baby.) Fertilization happens inside of the oviduct (aka Fallopian tubes). Therefore humans undergo internal fertilization. 35
FERTILIZATION Fertilization = sperm + egg The genetic information combines to form one human somatic cell with 46 chromosomes. 23 from mom and 23 from dad. The result is a zygote. This zygote will undergo mitotic divisions, doubling its amount of cells, keeping the same set of genetic information 36
As the cells continue to reproduce, they will eventually become specialized. This means that we start to see true gene expression; some will be turned on and others will be turned off. This allows cells to become specific things; heart cells, notochord, etc. The cell divisions are called "cleavage." 37
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Meiosis in Mom Meiosis in Dad 41