Sexual Reproduction

Question 1

General Features

Answer 1

~ generation of a new organism from 2 different organisms
~ only happens among same species
~ introduces new gene combinations and genetic diversity

Question 2

1. Fertilization

Answer 2

~ fusion of genetic material which belongs to 2 different cells
~ germ cells are located at sex organs
~ 2n primordial germ cells generate n gametes through meiosis
~ after fertilization two n germ cells, 2n zygote generates
~ zygote produces embryo with performing severall mitotic divisions and cellular differentiation
~ zygote produces somatic cells by mitosis as it developes into an adult
~ 23 + 23 = 46 chromosomes (2n)

Question 3

Generation of Gamete Cells

Answer 3

~ gametes contain a single member of homologous chromosome pairs
(Photos)

Question 4

Spermatogenesis vs Oogenesis

Answer 4

Spermatogenesis:
~ all produced gametes (sperms) gain fertilization ability

Oogenesis:
~ just 1 largest egg gamete can gain fertilization ability
~ its an important adaptation that the only biggest egg gamete gains the fertilization ability
~ primer oocytes stays at prophse I till puberty
~ when primer oocyte is triggered by hormones at puberty, meiosis continues
~ when seconder oocyte reaches metaphase II, meiosis stops
~ if sperm fertilize seconder oocyte, this triggers the completion of meiosis
(Photos)

Question 5

Zona Pellucida

Answer 5

~ a membrane which covers the surface of the oocyte
~ after sperm enters the oocyte, some vesicles in the oocyte secrete enzymes and turn zona pellucida into an impenetrable membrane (cortical reaction)
~ so only one sperm can fetilize the oocyte even though many sperms can reach it

Question 6

Why Every Person Is Unique?

Answer 6

~ prophase I, crossing over
~ anaphase I, homologous chromosomes line up randomly and seperates
~ egg sperm fertilization become randomly

Question 7

2. Conjugation of Bacteria and Paramecium

Answer 7

Bacteria:
~ bacterias transfer plasmids from f+ to f- by direct cell-to-cell contact through pillus and creation of cytoplasmic bridge
~ conjugation does not involve the fusing of gametes and the generation of a zygote, it can create an “alternative genetic variation” as it is necessary for the survival and adaptation to environmental changes
~ organism number do not increase after plasmid transfer like fertilization
Pillus: bacteria have a hair-like appendage found on their surface which ables bacterias attach to each other
Plasmid: acterias have small dna rings in addition to original circular bacterial dna
(Photos)

Question 8

Differences of Conjugation

Answer 8

Paramecium:
~ perform meiosis and endomitosis to create micronucleus
~ nucleus exchange between two paramecium

Bacteria:
~ do not perform meiosis
~ gene transfer happens to only one direction (from f+ to f-)

Question 9

3. Metagenesis

Answer 9

~ sporophytes (2n) consist spores underside of the leaves
~ spores (n) are generated by meiosis
~ gametophytes (n) generates from spores by mitosis containin both female and male sex organs
~ gametophytes are matureted to produce n gamete cells at different times in order to increase the chances of cross-fertilization and genetic variation
~ after fertilization of gametes, zygote generates and grows up by mitotic division to develope into a fern young plant called sporophyte

Question 10

4. Pollination

Answer 10

~ plants also have sexual reproduction besides asexual reproduction
~ plants cannot seek partners for themselves, so they use wind, water and insects to transfere pollens to female plant called pollination

Question 11

Parts of The Flower

Answer 11

~ male organ stamen
~ female organ carpel
~ petal: colorful part of the plant which attracts insects for pollination
~ sepal: usually green, protect seeds till germination
(Photos)

Question 12

Two Types of Pollination

Answer 12

1. If the pollens are transferred to the stigma of the same flower or another flower on the same plant, its called self-pollination. This type of plant is called hermaphrodite plants.
2. If the pollen graibs and transferred to the stigma of a different plant of the same species, the pollination is called cross-pollination. If a plant has only male organ, this plan is male plant. If a plants has only female organ, its a female plant.

Question 13

Fertilization

Answer 13

A pollen grains on the stigma grows a tiny tube all the way down through style to the ovary. At this pollen tube, pollen divides into 2 sperms before reaching the ovary. (Photos)

Question 14

Double Fertilization

Answer 14

~ one of the generated sperms (n) meets with egg cell (n) inside the ovary and generates zygote (2n)
~ the other sperm meets with 2n polar nucleus and generates triploid 3n endosperm
~endosperm feeds seeds till germination

Question 15

Invertebrate and Vertebrate

Answer 15

Invertebrate: arthropod (lobster, spider, scorpion, insects)

Vertebrate: fish, amphibi, bird, reptile, mammalia also make sexual reproduction

Question 16

Hermaphrodite

Answer 16

Some animals and plants have both male and female reproductive system, they are called hermaphrodite ex: earth worm

There are some mechanisms to prevent self fertilization of this organisms in order to increase the genetic diversity.