Biology (Unit 2: Reproduction) Flashcards
Sexual and Asexual Reproduction
Sexual:
- Reproduction requiring male and female parent and involves the fertilisation of sex cells (gametes)
- Allows for more genetic diversity and better adaptability to environment
Asexual:
- Reproduction that only requires one parent, leading to genetically identical offspring
- Leads to quicker and more efficient reproduction with more offspring but at the cost of genetic divesity
Stages of cycle
Interphase:
- Resting phase between successive divisions of mitosis and meiosis
- Includes Consists of gap 1, synthesis, gap 2, and gap 0
Gap 0:
- Rest phase
- No division nor preparation for division mechanism
- Cells may leave gap gap 1 to go to gap 0
- Involves growth and differentiation
Gap 1:
- First stage of interphase
- Cell growth and significant increase in size takes place
- Production of RNA and proteins in preparation for mitosis
- Chekcpoint: if cell is big enough and environment is suitable, it progresses to synthesis
Synthesis:
- DNA synthesis, AKA replication takes place
- Creates two copies of each chromosome, making 46 chromosomes of 2 chromatids instead of one each
- Also replicates centrioles, making 4 instead of 2
Gap 2:
- Cell continues growth
- Continues producing new proteins
- Chekcpoint: if DNA replicated, cell size large enough, and environment suitable, cell progresses to mitosis
Mitosis:
- Cell divides
What is mitosis?
- Process where new identical cells are produced for growth, replacing damaged/old cells, and asexual reproduction
- Happens in most areas of the body
How it works:
- Cell is diploid as it has 23 homologous pairs of chromosomes
- Has 46 chromosomes each with two chromatids
- Cell divides into two cells and still has 46 chromosomes but each with one chromatid
Stages:
Prophase:
- Chromatin condenses into chromosomes
- Nuclear membrane begins to break down along with nucleus
- Centrosomes migrate to poles
Metaphase:
- Chromosomes line up centromeres on equator of cell
= Centrosomes form spindles and attach to centromeres of each chromosome
Anaphase:
- Each chromosome is split
- Each side is pulled to opposite side of cell
Telophase:
- Nuclear membranes begin reforming
- Chromosomes cluster in center of new cells as cell begins to separate
Cytokinesis:
- Remaining spindle fibers break down
- Cytoplasm is divided, separating cell into 2 daughter cells
- Same number of chromosomes as parent cell
What is meiosis?
Explain the male reproductive system and how it works.
- Testes make male gametes called sperm/speratozoa; there are 2 of them
- Testes are outside body in 2 sacs of skin called the scrotum
1) Sperm go from each testis to tube called sperm duct
- Sperm duct joins with urethra below bladder
- Urethra continues until tip of penis
- Urethra transports sperm at different times
- Prostate gland is at point where urentra and sperm duct connect, making fluid which sperm flow in
- Sperm are made in tubes or tubules in the testes from the cells in the walls of them which then divide by meiosis
- Stored in tube of epididymis
Explain the female reproductive system and how it works.
- Ovaries make female gametes called eggs; there are 2 ovaries
- The girl will have had thousands of them before puberty and by then, one will begin to mature
- Leading away from them are oviducts/fallopian tubes
- 2 oviducts lead to uterus/womb
- Uterus is small but has thick, muscular walls that can stretch a lot to house the baby when the woman is pregnant
- Cervix is pack of muscles guarding entrance to uterus
- Leads to vagina which is open to the outside
Explain ovulation
- When a girl reaches puberty, her eggs begin to mature with one developing at a time
- When mature, an ovary bursts out of its follicle in the ovary and into the oviduct in a process known as ovulation
Explain fertilization
- After ovulation, the egg is caught in the funnel of the oviduct
- The cilia waft the egg cell through the tube towards the entrance
- The egg slowly travels towards the uterus with cilia and the muscles involved in peristalsis moving the egg along
- Only one sperm can enter the egg, with only its head entering and the nucleus fusing with the egg cell
Explain implantation
Explain the menstrual cycle
- Female’s way of preparing for reproduction and is a 28 day cycle
- Day 1: period (menstruation) expels lining of uterus along with the gamete
- Between days 5 - 14, endometrium thickens
- Egg cell is released on day 14
- Egg has 3 days to be fertilised, otherwise it dies
- If egg is not fertilised, the endometrium begins to break down between day 18 and 28
- Cycle repeats
Explain how hormones work during the menstural cycle
FSH (Follicle Stimulating Hormone):
- Stimulates swelling of egg cells in follicles
- Produced by pituitary gland
Oestrogen:
- Stops production of FSH to prevent another egg cell from maturing
- Thickens uterus lining
- Stimulates release of LH
- Produced by ovary
LH (Lutinizing Hormone):
- Used to make follicles burst and cause ovulation
- Produced by pituitary gland
Progesterone:
- Produced by Corpus Luteum
- Maintain endometrium
- Corpus luteum is made by bursting follicle but gradually degrades unless it receives a message from the embryo
- Increase in oestrogen and progesterone leads to reduction in LH and FSH
Human Chorionic Gonadotrophin (HCG):
- Circulates blood stream
- Maintains the corpus luteum so it keeps producing progesterone to maintain the endometrium
How do hormones work in contraceptive pills?
Explain how the placenta works
