Lecture 4: The alternation of generations Flashcards
what are gametes?
sexual cells that can fuse to form a diploid zygote
what is a zygote?
a cell formed by the fusion of 2 gametes
what are isogametes?
complementary gametes that look similar (sperm - small, motile, male & eggs - large, immobile, female)
what are anisogametes?
complementary, motile gametes that look different (smaller = male & larger = female)
what is syngamy?
the fusion of 2 complementary gametes to form a zygote
what is gonidium?
an asexual reproductive cell/ group of cells where reproductive cells are produced
what is a gametangium?
sexual tissues in which gametes are formed from
what is a spore?
a haploid cell that can give rise to a new individual without syngamy
what is a zygospore?
a diploid cell formed by the fusion of 2 gametes
what occurs when the zygospore undergoes meiosis?
forms haploid cells that generate gonidia
what is a gametophyte?
a haploid plant that produces haploid gametes by mitosis
what is a sporophyte?
a diploid plant that produces haploid spores by meiosis
what is a sporangium?
the tissues in which haploid spores are formed
what are homospores?
spores that are identical in size and morphology BUT will form male or female gametophytes
what is a zoospore?
motile spore
what is a sporophyll?
a leaf (microphyll) that bears a sporangium
what is an archegonium?
female parts of the gametophyte (where egg cell is located)
what is an atheridium?
male parts of the gametophyte
how to chlorophytes reproduce?
vegetative mitosis
what is the process of vegetative mitosis?
- when under environmental stress, unicellular chlorophytes differentiate to behave as gametes (become motile if not already)
- isogametes pair and fuse becoming a zygote
- zygotes undergo meiosis becoming genetically recombined haploid cells
what occurs as chlorophytes become colonial?
gametic dimorphism where male (smaller) and female (larger) gametes are obvious
what is oogamy?
larger gametes losing the ability to be motile and look like eggs
what is volvox?
a model colonial chlorophytic cell that has differentiation of somatic and sex cells
how do cells lose their immortality?
as cells reproduce via meiosis differentiation occurs meaning mother and daughter cells no longer are the same so ‘death’ is introduced