MODULE 5: HEREDITY Flashcards
INQ 1.1
Sexual Reproduction
The fusion of a gamete (sperm and egg) from both parents to produce a genetically unique offspring.
INQ 1.1
Asexual Reproduction
Reproduction requiring only one parent and produces an offspring that is genetically identical to a single parent (unless mutations occur).
INQ 1.1
Internal Fertilisation
The fertilisation of an egg and a sperm inside the body of a female.
- male transferring his gamete (sperm) into directly inside a female’s reproductive tract to fertilise her gamete (egg)
INQ 1.1
Continuity of Species
The ability of a species to persist over time through reproduction, ensuring that genetic information is passed on to subsequent generations.
INQ 1.1
External Fertilisation
A male depositing his sperm on a female gamete (egg) outside of the female’s body.
INQ 1.1
How does sexual reproduction ensure the continuity of a species?
- The combination of chromosomes from two organisms increases genetic variability
- This assists with a species survival, as it allows for them to be able to adapt to changing environments
INQ 1.1
Advantages of External Fertilisation
- a large number of gametes is dispersed at a time = higher number of offsprings produced - increased genetic variation
- No need to find a mate - easier fertilisation process and time efficient
- usually more rapid and prolific
- no energy is needed for gestation and caring for young
- as the young is widely dispersed, compeitition is reduced with the parent and each other
INQ 1.1
Advantages of Internal Fertilisation
- increased liklihood of fertilisation as the two gametes are in close proximity to each other.
- increased protection of offspring from the outside environment = increased survival rate
- Protects the gametes from being dehydrated on land
- Developed young is taken cared for and fed, increasing chances of survival
- gametes and zygote is protected from predation and diseases.
INQ 1.1
Disadvantages of External Fertilisation
- recquires an aquatic environment
- no protection is given to the eggs (vulnerbale to predators)
- large number of gametes = takes time and energy
- no control on how many gametes released
- decreased chance of successful fertilisation
- young needs to fend for themselves
INQ 1.1
Disadvantages of Internal Fertilisation
- longer gestation period
- time and energy is needed to care for young after birth
- potential for STIs
- energetically costly for both parents
INQ 1.1
How do plants reproduce?
- Sexual reproduction: pollination (transfer of pollen from anther to stigma of plant)
- Asexual reproduction: vegetative propagation (bulb, rhizome, runners, sucker, tuber)
INQ 1.1
Advantages of Sexual Reproduction
- fertilisation is less risky (controlled env. and protection); young are more likely to survive
- unfavourable genetic traits can be eliminated
- more genetic diversity
- able to adapt to changing environments
- improves the evolutionary potential of populations
this all allows for the continuity of species
INQ 1.1
Disadvantages of Sexual Reproduction
- slower reproductive rate
- mates need to be found and accepted
- recombination during meiosis can introduce deletarious variation
- potential for STIs
- energetically costly
INQ 1.1
Advantages of Asexual Reproduction
- energy efficient (no mate)
- passing on of favourable traits
- fast rate of reproduction
– rapid rate of repopulation
– short gestation period
– good if selection pressure is posed and species need to repopulation before extinction
INQ 1.1
Disadvantages of Asexual Reproduction
- little to no genetic variation
– risk of extinction if selection pressure is posed - faster rate of repopulation
– increases compeition (decreases population of other species in the food web)
INQ 1.2
Fertilisation
the fusion of a male haploid gamete (sperm) and a female haploid gamete (ova) to form a single dipoloid zygote cell.
INQ 1.2
Process of fertilisation in humans
- enzyme from sperm dissolves and penetrates into the zona pellucida surrounding the egg
- sperm binds to the receptors on the egg cells membrane, fertilising the egg
- nucleus of the sperm enters the cytoplasm in the egg
- the eggs surface area is chanfed to prevent the entry of multiple sperm nuclei into the egg
- fusion of the haploid egg and sperm nuclei creates a diploid zygote cell (fertilised egg)
INQ 1.2
Implantation
The attachment of the blastocyst on the unterine wall (or endometrium)
INQ 1.2
Hormones
chemical substances which regulates and controls the functioning of cells or organs
Hormones are released by the pituitary gland
INQ 1.2
The process of Hormone Release in the Mentrual Cycle
- GnHR (gonadotropin-releasing hormone) signals the pituitary gland to release FSH and LH.
- FSH increases for the development and maturation of ovarian follicles which starts to develop
- FSH increases oestrogen levels for ovulation
- the rise in oestrogen sends a positive feedback loop and causes the surge of LH and FSH production
- the peak in LH and FSH triggers ovulation
- Progesterone is released by the corpus leteum (stimulated by LH)
- Progesterone thickens the uterus lining (to prepare for implantation) and inhibits the production of FSH and LH (to prevent more eggs / follicles from developing)
- If no pregnancy, then the corpus luteum will break down and degenerate, causing the drop in progesterone and estrogen levels
- This triggers the shedding of the uterine lining (menstration), and marks the start of a new cycle.
- GnHR (gonadotropin-releasing hormone
- FSH (follicle-stimulating hormone)
- LH (Leutinizing hormone)
- Corpus Luteum: temporary collection of cells that forms in the ovary after ovulation
INQ 1.2
The hormones in pregnancy
From the mentsrual cycle, if fertilisation does occur:
* the blastocyst (developing embryo) will release HCG.
* this allows for the maintainence of the corpus luteum, allowing for the continued secretion of progesterone and oestrogen.
* these two hormones are essential in maintaing the uterus lining to support embryonic development.
HCG: human chorionic gonadotropin
INQ 1.2
Prolactin
Stimulates lactation, and maintains milk production
