reproduction; sexual reproduction/meiosis

Question 1

sexual reproduction

Answer 1

creation of offspring through process of fertilization–fusion of two gametes

Question 2

meiosis

Answer 2

special type of cell division that occurs only in reproductive organs
makes reproductive cells called gametes (egg and sperm)

Question 3

what are the two functions meiosis serves?

Answer 3

-halving chromosome number
-producing genetic variety

Question 4

with sexual reproduction hypothetically…

Answer 4

we can thrive even with the change in environment as at least one of us will be born with genetic variants that can overcome the changes.

Question 5

chromosome number

Answer 5

all cells in human body but gametes have the same amount of chromosomes: 46

Question 6

diploid(2n)

Answer 6

number of chromosomes&raquo_space; 46

Question 7

haploid(n)

Answer 7

gametes need the number to be cut in half» 23 chromosomes (haploid)
to produce viable offspring
g a m e t e s c o n t a i n o n l y o n e o f e / t y p e o f
c h r o m o s o m e t h a t d i p l o i d p a r e n t c e l l s c o n t a i n s

Question 8

phase of meiosis

Answer 8

1. meiosis i&raquo_space; reduces chromosmes from diploid to haploid, known as: reduction division
2. meiosis ii&raquo_space; further divides the cell

Question 9

interphase

Answer 9

cell grows and replicates DNA
after replication e/ chromosome is made up of a pair of identical sister chromatids held together by centromere

Question 10

prophase i

Answer 10

homologous chromosomes contain the same genes, as they come from different parents, they can have different alleles
-nuclear membrane disappears
-spindle fibers start forming
- c r o s s i n g o v e r o c c u r s

Question 11

crossing over role

Answer 11

to exchange the genetic materials between non sister homologous chromatids

Question 12

crossing over process

Answer 12

during formation of bivalent, non sister chromatids may touch and break. two segments may rejoin at the some position of chromatid within the region: chiasma.

Question 13

crossing over process forms

Answer 13

chromatid which becomes: a mixture of paternal and maternal alleles

Question 14

crossing over other ending

Answer 14

this event may occur multiple times between different chromatids within the same homologous pair&raquo_space; some alleles never form a chiasma

Question 15

metaphase i

Answer 15

spindle fibers attach to centromere of e/ chromosome
pull e/ bivalent to center of the cell
r a n d o m a s s o r t m e n t o c c u r s

Question 16

random assortment

Answer 16

bivalent line up on the equator of the cell randomly

Question 17

random assortment end result: parallel

Answer 17

paternal chromosomes could both line up together one one side w/ maternal on the other

end results for gametes: some will contain maternal chromatids while other will contain paternal chromatids

Question 18

random assortment end result: together

Answer 18

maternal + paternal chromosomes could be on both sides of equator

end results for gametes: all contain a mixture of maternal + paternal chromatids

Question 19

anaphase i

Answer 19

homologous chromosomes separate + move to opposite poles of the cell
centromere doesn’t split&raquo_space; sister chromatids are still held together
moving one chromosome to e/ pole

Question 20

telophase i

Answer 20

(doesn’t occur in all cells)
when occurs&raquo_space; chromosomes begin to coil = spindle fibers disappear, cytoplasm divides + nuclear mb is formed around the homologous pair of chromosomes

Question 21

telophase i why does it go straight to prophase ii

Answer 21

as e/ chromosmes already consists of two chromatids, DNA replication doesn’t need to occur between telophase i and prophase ii

Question 22

prophase ii

Answer 22

nucelar mb disappears
chromatin coil turns invisible

Question 23

metaphase ii

Answer 23

spindle fibers attach to centromere of e/ chromosome
spindle fibers moves chromosomes to the middle of the cell

Question 24

anaphase ii

Answer 24

spindle fibers pull sister chromatids to the opposite poles of cells

Question 25

telophase ii

Answer 25

nuclear mb reappears, spindle fibers disappear, cytoplasm divides and new cells are formed

end result: 4 non-identical haploid cells

Question 26

dual reproductive system

Answer 26

uses asexual reproductive system when there’s
-ample food
-H2O = favourable for rapid growth and development
switches to sexual when
-food lessens/less humidity in environment
-lasts until winter
ex: starlet sea anemone

Question 27

sexual disadvantages

Answer 27

a problem for non-mobile animals/animals who live in solitude as they can’t find a mate
solution hermaphroditism&raquo_space;both female and male reproductive organs, when mating both get pregnant (still need to mate) & twice as many offspring.

Question 28

internal fertilization

Answer 28

sperm deposited in or close to female reproductive tract for gametes to unite
occurs in terrestrial animals

Question 29

internal fertilization requires…

Answer 29

copulation/sexual intercourse
meaning it requires complex reproductive system and organs that facilitates copulation

Question 30

external fertilization

Answer 30

When male and female gametes are discharged -> water which is where fertilization occurs
occurs in aquatic vertebrates: fishes + amphibians