Multicellularity and Sex Flashcards
multicellularity
usually means different cell types that interact with each other to build organism structure
sex
involves change in ploidy during life cycle
which clades are multicellular
fungi, animals, red algae, land plants, brown algae
is multicellularity an inevitable evolutionary transition?
nah bro
earliest multicellular organism date
580 mya (prob animal)
costs and benefits to multicellularity
costs- energy and physiological probs (like diffusion across many cell layers)
Benefits- persistence and dominance in habitat
-structural complexity enables multiple solutions to complex problems
what was the atmospheric requirement for multicellularity?
oxygen
plant cell adhesion
plasmodesmatas
animal cell adhesion and communication
cell junctions
chem signaling and electrical signaling
usually one cell will secrete a hormone that’ll bind to receptors on another cell
electric potentials (e.g. mimosa plant)
is sex an old or a new eukaryotic trait?
Sex was in the early eukaryotes
do prokaryotes have sex?
nah bro
2 processes in sex
meiosis and fertilization
4 steps differing meiosis from mitosis
- pairing of homologous chroms.
- recombo of non-sis chromatids
- suppression of sister-chromatid separation during first division
- no chrom. replication during 2nd meiotic division
anisogamous species
- gametes aren’t identical
- some have flagellated gametes
- include oogamous ones
- plants, animals, and many protists
oogamous
sperm producer is male and egg producer is female
isogamous
morphologically identical gametes (lots of protists and fungi)
chromosomal sex determination
- Sex chromosomes: homogametic (xx) and heterogametic (xy)
2. Ploidy level: haplodiploid where diploid=f and haploid=m
environmental sex determinations
- temp during development
2. population-density chems during dvlpmnt
Dioeciou/Gonochoristic
one sex only throughout life–> male of female
Hermaphrodite/ Monoecious
both sexes at once –> in plants–> depends on how flowers are made
sequential hermaphrodite
both sexes at dif times in life
example of haplodiploidy
bees
can something be oogamous and hermaphroditic at the same time?
yeah bro
parrotfish
protogynous
- start female (usually)
- terminal phase males develop from females
- turn red
clownfish
- protandrous
- start male
- big dom male becomes female
- she only mates with 2nd biggest
pros and cons of hermaphrodite
pros: ease of finding sex partner, whether yourself or someone els
cons: offspring’s alleles only come from you
- loss of heterozygosity
- more deleterious recessive alleles
how do hermaphrodites avoid self-fertilization?
earthworms only exchange sperm with other individuals
plants often have self-recognition proteins that prevent self-gametes from growing
Can eukaryotes reproduce asexually
yep
describe the ploidy changes in asexual reproduction
there aren’t any
parthenogenesis (animal)/ apomixis (plants)
usually female ofspring are formed from egg of mother –> genetic clones
-dandelions, nematodes, amphibians, sharks, etc…
vegetative reproduction
body pieces of parent become free liing
- clones
- ex: medusae from hydrozoan animals and alot of plants
marbled crayfish (p. virginalis)
triploid females make female young parthenogenetically
-only decapod crustacean that can do that
Dominant stages are haploid
haplontic life cycle with zygotic meiosis
dominant stages are diploid
diplontic life cycle with gametic meiosis
alternation of haploid and diploid life stages
- alternation of generations
- diplohaplontic life cycle with sporic meiosis
