inquiry question 1 mod 5 Flashcards
reproduction
production of new offspring
- asexual
- sexual
heredity
the passing of characteristics from one generation to the next through genetics through DNA which is located in the cells nucleus
sexual reproduction
requires the combination of genetics from two individuals to create genetically different individuals
- meiosis
- fuses to form 2n zygote
asexual reproduction
requires one individual to create genetically identical offspring
- mitosis
eg. binary fission, budding, fragmentation, regeneration
eg. starfish,
advantages to asexual reproduction
-Does not place a great energy demand on the organism
- Mate isn’t required
- Offspring can disperse easily to colonise new areas
- Reduces competition for resources → increases survival chances for the parent and offspring
- Reproduce very rapidly → don’t have to wait for fertilisation or the growth of the embryo
disadvantages to asexual reproduction
- No genetic variation
- Dangerous mutations in DNA are passed down
different asexual reproduction methods and examples
- Vegetative propagation → Budding, cutting, layering, grafting → eg. plants, protists
- Binary fission → eg. bacteria, protists
- Fragmentation
- Regeneration
- Parthenogenesis
cutting
part of stem is cut and planted in the soil, gradually growing into another plant
layering
Branch of plant bends down into the soil and develops its own roots while attached to parent plant
grafting
- Two plants are selected and the stem of the base plant (stock) is cut and the other plant cutting (scion) is joined on
- The scion grows into the fruit and flowers
budding + process
when offspring grows off the body of the parent which is identical to the parent eg. fungi, tapeworm
- after breaking off the organism is independent
process:
1. small protrusion on the parent cell grows to form a bud
2. nucleus of parent cell splits –> produces a daughter nucleus –>migrates to the new cell
3. bud pinches off the base –> detaches from the parents base
4. process repeated to form a chain of buds
sporation
through asexual and sexual reproduction sexual spores produce a fruiting body eg. fungus
process:
1. spores grow long hyphae through budding
2. different hyphae meet –> conjugate –> combine genetic material (sexual)
3. produces diploid (2n) fungus –> matures to form a fruiting body
4. process restarts
binary fission
Asexual reproduction of two identical daughter cells eg. bacteria, protists
process:
1. Bacterium contains tightly wound DNA
2. DNA is replicated
3. Each copy of DNA moves to opposite ends of the bacterium as it increases in size
4. A cell wall begins to form in the centre of the bacterium
5. New cell wall completely splits the bacterium in half
6. The new daughter bacteria are complete with DNA, ribosomes and plasmids (tightly wound)
pathogenesis
females produce eggs which develop into young without being fertilised eg. some insects (bees), some fish
- no increase in genetic diversity –> the offspring are genetically identical to the parent
fragmentation
Allows an adult to break up into two or more pieces in order to produce exact copies of itself eg. flatworms
- fragments develop into mature adults
regeneration
If part of the animal if broken or cut off from an individual → the part can develop into a new individual if the body part contains enough genetic information from the parent
advantages to sexual reproduction
- Diverse offspring due to genetic variation –> Better chance of survival from harsh environments
- Plants can resist disease
- Selective breeding –> used to develop plants and animals with desirable traits
disadvantages to sexual reproduction
- Time and energy
- Organisms have to grow and develop until they can produce sex cells
- Searching for a mate may expose the individual to predators, disease or harsh environmental conditions
- Needs to find a mate to be fertilised
- Fertilisation cannot take place during pregnancy → for some mammals it lasts 2 years
fertilisation
Fusion of two sex cells eg. sperms and eggs (gametes) to form a diploid zygote
- union of two haploid (n) gametes → restores the chromosome number back to normal →
- external
- internal
external fertilisation
egg fertilised outside the female’s body
- Male and female gametes are released into the species surrounding → some will fuse to form a zygote
- requires a moist environment
eg. fish
zygote
the first cell of a new organism
why does external fertilisation require a moist environment
- Prevents the desiccation of gametes
- Provides a medium of transport
how do animals overcome issues during external fertilisation
- mass spawning
- timing release of gametes
- frogs have complex mating behaviours
internal fertilisation
eggs are fertilised by the sperm inside the females body through specialised functions in the male
- male and female must be in close proximity
- males have specialised copulatory organs (penis)
example of male specialised copulatory organ
penis
stages of the reproductive cycle
- internal fertilisation
- implantation of embryo
- pregnancy
hormones
chemical messengers of the body
pituitary gland
stimulates endocrine glands that control the secretion of hormones
oestrus
fertile
advantages and disadvantages of internal fertilisation
advantages:
- high probability of successful fertilisation
- less gametes needed
- external water source is not needed
disadvantages:
- organisms need to be in close proximity
- energy demands to find mate and protect offspring is high
- few offspring can be produced
advantages and disadvantages of external fertilisation
Advantages
- Offspring can disperse easily
- Mate is not required
Disadvantages
- Gametes may be eaten by predators
- strong currents can sweep them away
hermaphrodite animals
organism that produces both female and male gametes
parts of the male reproductive system
semen
urethra
testes
scrotum
epididymis
penis
prostate gland
seminal vesicles
vas deferens
testes
structure: oval structure
function: responsible for secreting the hormone testosterone and produces sperm
semen
sperm + prostate fluid exists body via urethra
penis
structure: the organ used for urination and sexual intercourse, contains the urethra
function: Spongy tissue → can fill with blood to cause an erection
scrotum
structure: loose bag of skin that hangs outside the body behind the penis
function: holds testes in place and keeps sperm at a lower temperature
epididymis
structure: highly coiled tube that lies at the back of the testes
function: all sperm must pass through this structure where they mature and start to swim
vas deferens
structure: thick walled tube joined to the epididymis
function: carries sperm from the epididymis up to the prostate gland and urethra
prostate
produces fluid secretions that support and nourish the sperm
urethra
structure: Tube that extends from the bladder to the external opening at the end of the penis
function: carries both urine and sperm (gametes)