D3 Continuity and Change : Organisms Flashcards
Reproduction, inheritance and homeostasis
hermaphrodites
An organism with both male and female reproductive organs.
what makes up the menstrual cycle
ovarian and uterine cycle
3 stages of ovarian cycle
- follicular phase
- ovulation
- luteal phase
3 stages of uterine cycle
- menstruation
- proliferation phase
- secretarial phase
double fertilisation
The two fertilisation events that occur: fusion of the first male gamete with the nucleus of the egg cell, and the fusion of the second male gamete with the two polar nuclei present in the central cell.
self- incompatibility
The inability of hermaphroditic plants to produce zygotes after self-pollination.
germination
The process that begins with the uptake of water by the seed and ends with the emergence of the radicle.
Gametogenesis
Formation of haploid gametes - spermatogenesis and oogenesis
corpus luteum
A temporary organ formed in each menstrual cycle from the ruptured follicle which secretes hormones.
zona pellucida
A layer on the outside of the oocyte made of glycoproteins. It is present in the unfertilised cell as well as in early embryo development.
corona radiata
A layer of follicular cells that surrounds the ovum.
acrosome
An organelle at the head of the sperm that contains digestive enzymes that aid fertilisation.
capacitation
Biochemical and physiological changes undergone by the sperm in order to fertilise an egg.
triple fusion
The fusion of a single male gamete with the two polar nuclei present in the central cell.
endosperm
Tissue that surrounds the developing embryo of flowering plant seeds and nourishes them.
acrosome reaction
Hydrolytic enzymes released by the acrosome digest and soften the zona pellucida, assisting fertilisation.
polyspermy
The fusion of more than one sperm with the egg.
cortical reaction
A mechanism that prevents polyspermy and involves the release of cortical granules from the fertilised egg.
cleavage
A series of rapid cell divisions undergone by a zygote.
trophoblast
Cells that will become the placenta
inner cell mass
Cells within the blastocyst that will become the embryo.
haploid
A haploid nucleus contains a single set of chromosomes. Gametes are haploid.
diploid
Cells that contain two copies of each autosome and two sex chromosomes. Diploid cells have an even number of chromosomes.
self pollination
The transfer of pollen grains to the stigma of the same flower or to the stigma of another flower on the same plant.
cross pollination
The transfer of pollen grains from one flower on one plant to the stigma of another flower on another plant.
P generation
Parent generation of a genetic cross.
F1 generation
F1 are the offspring from the P generation; F2 are the offspring produced from crossing F1 parents.
homologous chromosomes
A pair of chromosomes of the same type (one comes from the mother and one comes from the father).
allele
A variant or version of a gene.
phenotypical plasticity
The ability of an organism to exhibit variations in its physical characteristics or traits in response to environmental influences.
codominant
Two alleles are both expressed equally.
incomplete dominance
A third phenotype that is intermediate between the dominant and recessive can be produced.
non disjunction
The failure of homologous chromosomes or sister chromatids to separate during cell division.
sex linked genetic disorders
A condition caused by a mutation on the X chromosome.
gene pool
The combination of all the genes that are present in a reproducing population.
discrete variation
Phenotypes that have distinct categories, for example, blood type A, B, AB or O.
polygenic inheritance
When more than one gene controls a characteristic, for example, the inheritance of skin colour.
continuous variation
Phenotypes that show a wide variety between two extremes in a population, for example, height.
linked genes
Genes on the same chromosome that are usually inherited together.
unlinked genes
Genes on different chromosomes that assort independently.
independant assortment
The separation of homologous chromosomes and sister chromatids being independent of their pair during meiosis due to random orientation.
monohybrid cross
A cross between two individuals of the same species that considers the inheritance of a single trait.
dihybrid cross
A cross between two individuals of the same species that considers the inheritance of two traits.