Final Flashcards
2 principle modes of animal reproduction:
Sexual and asexual
Asexual
1 parent Usually mitosis No fusion of gametes 2n➡️2n Genome of parents & offspring identical
Sexual
2 parents usually meiosis Fertilization 2n➡️1n➡️2n Genome of parents & offspring different
Types of asexual reproduction
Fission
Budding
Fragmentation
Parthenogenesis
Fission
🌳separate into 2 or more indi of equal size.
🌳Common among bacteria and protists
Fragmentation
🌳parent breaks into smaller pieces followed by regeneration
🌳synonym= architomy
🌳tapeworms, sponges, Cnidaria, polychaetes, tunicates
Budding
🌳small India splits from parents 🌳Common in colonial animals 🌳often wlout separation 🌳paratomy=transverse or linear budding 🌳Annelids and platyhelminthes
Parenthogenesis
🌳egg deve wlout fertilization
🌳highly variable and widespread condition
🌳2 basic mechanisms
🔥Haploid egg develops into haploid adult
🔥Chromosome number doubles to create diploid zygotes
🌳gamete formation also variable (meiosis or mitosis)
Advantages of asexual reproduction
🌳reproduction w/o mates (energy and risk reduction)
🌳rapid rates of pop increase
🌳rapid colony growth
🌳Perpetuation of successful genotypes
Sexual reproduction
🌳The formation of a new individuals following the union of 2 gametes
🌳char by 2 processes
🔥gamete formation: meiosis (2n➡️1n)
🔥fertilization-fusion of 2 gametes (syngamy): 1n➡️2n
🔥🔥ova- usually large and nonmotile
🔥🔥sperm- usually small and motile
Reproductive Cycle and Petterns
- cycles tend to be seasonal and attuned to specific environmental cues
- great variety in life history
- > hermaphroditism: m and f in the same body
- common in sessile, burrowing, and parasitic animals
- widely dispersed in animals
- adv: doubles reproductive chances/output
- disadv: energetically costly
Population
a group of indi of a single species that simultaneously occupy the same general area
unit of natural selection
2 important char of population
density
dispersion
density
number of indi per unit area
rarely can density be counted directly
not a static property (migration)
dispersion (3 types)
pattern of spacing among indi
Clumped
Uniform
Random
Clumped
most common
aggregation into patches
heterogeneous (patchy) distribution of key env factor
—organisms dwelling in decaying logs (humidity)
—tide pool organisms (reduced competition, food)
mating aggregations
social aggregations (herds, schools, packs)
Uniform
Even spacing
direct interactions among indi
—germination-inhibiting compounds
—antagonistic social interactions
Random
unpredictable spacing
least common
position of an indi is indep of other indi
absence of strong attractions or resulsions
Demography
study of the vital statistics that affect the pop size by birth rate death rate generation time sex ratio summarized with life tables
Survivorship Curves
plot of the proportion or numbers of a cohort still alive at each age
log scale at Y
variables tend to fall into one of 3 patterns
3 patterns of SC
type I: low infant thru midlife midlife mortality
type II: constant death rate over the lifespan
type III: high juvenile mortality rates
demographic studies often ignore males
in sexually reproducing species, only f produce offspring
NS favors traits that
+ survivorship
+ reproductive success
life history
the traits that affect an organism’s schedule of reproduction and death
