Topic #2 Animal Reprod.+Devp.+Form+Function Flashcards
What are the 2 Mechanisms of Reproduction?
a) Sexual:
- 1/2 of alleles passed (sacrificed to get variation)
- gametes required
- variation
b) Asexual :
- single parents (usually females)
- gametes optional
- little variation
Examples of Asexual Reproduction
Budding= Offspring grows off you
Fission= Animal splitting into 2 animals
Parthenogenesis (Virgin+Creation)= female can Reprod. without fertilization). Asexual Reprod. in which an egg develops without being fertilized.
Examples of Parthenogenesis (Virgin+Creation)
a) Bees and Wasps -> Queen stores sperm and determines when egg+sperm fertilize and if male/female. Offspring can be diploid or haploid. Haploid males drones arise from parthenogenesis vs females which are diploid adults that arise through fertilization
b) Whiptail Lizard -> Undergoes a modified form of telophase. Starting off with (diploid) 2N=4 segueing to 4N=8 (tetraploid) during mitosis due to the formation of a single nuclear envelope around all 8 XMs which become DIPLOID daughter cells/eggs (Not haploid)!!!
What are the two triggers of Whiptail Lizard ovulation?
a) Hormonal b) Behaviour (When population is mostly female)
- High Estradiol levels cause female lizard to behave like a female (Takes it) and releases eggs
- Once Estradiol levels drop, Progesterone levels increase causing the lizard to take over the male role (mimics copulation act of male)
What is the two separation of sexes?
a) Dioecious (2 houses)= female house (ovaries) and male house (testes)
b) Monoecious (1 house)= Hermaphrodites (has both male and female sexual organs)
What are the 3 types of Hermaphroditism?
a) Simultaneous Hermaphrodite= male and female sexual organs both work which makes it able to fertilize itself
b) Mutual cross fertilization= no need for male/female b/c both organisms can act as male or female
c) Sequential Hermaphrodite= Changes sex throughout life
- Protandry (start off as male then becomes female)
- Protogyny (start off as female then becomes male)
List the order of Gametogenesis
a) Primordial Germ Cell MITOSIS b) "Spermato/Oo"->\_\_\_gonium MITOSIS c) Primary "Spermato/O"->\_\_\_cyte MEIOSIS I d) Secondary "Spermato/O"->\_\_\_cyte MEIOSIS II e) "Spermato/O"->\_\_\_tid Maturation f) gamete
What are some of the differences between sperm and egg formation during Gametogenesis?
Sperm
a) equal division during meiosis I and II which leads to equal daughter cell size
b) 4/4 daughter cells become functional gametes
c) Process starts @ puberty and is ongoing
Eggs
a) unequal division during meiosis I and II which leads to unequal daughter cell size (purpose is to make one egg full of yolk)
b) 1/4 daughter cells become a functional gamete
c) process starts in Utero -> pauses @ birth (reaches up to Oocyte) -> resumes at puberty -> each egg released @ puberty during ovulation is a secondary Oocyte -> pauses again until secondary Oocyte is fertilized -> continues until menopause
What are the 3 different types yolk amounts and distribution?
Yolk is rich in fat and protein granules located in the cytoplasm
a) Isolecithal (equal-yolk)= small amount of yolk evenly distributed throughout cytoplasm of ovum
b) Mesolecithal (intermediate-yolk)= intermediate size yolk concentrated on one hemisphere of egg
c) Telolecithal= lot of yolk evenly distributed
What’s the purpose of different yolk distribution?
- The yolk is “energetically expensive” to prod.
- More yolk= more food for embryo= precursor to amount of time required for embryo to develop before transitioning into larval stage
Acrosomal Reaction
The discharge of hydrolytic enzymes from the Acrosome (a special vesicle at the tip of the sperm) which partially digest the protective-jelly coat of ovum. This allows passage of the sperms Acrosomal Process to elongate and bind to specific protein receptors that stick out from the Ovum’s plasma membrane= Molecular Recognition that prevents hybridization
2 Steps to Fertilization
a) Membrane Fusion= Male pronucleus is now in the same cytoplasm as female pronucleus which triggers the secondary Oocyte to finish meiosis II (large ovum released and smaller second polar body ejected)
b) Nuclear Fusion= Large ovum unites with sperm to form diploid zygote
Cortical Reaction
A reaction when cortical granules move up into vitelline space and release contents which play with tonicity allowing water to rush in create a fertilization envelope preventing sperm from entering ovum
2 Ways to Prevent Polyspermy
a) Fast Block (1-2 sec)= occurs upon contact of first sperm which is positively charged and attracted to negatively charged ovum interior. As soon as 1st sperm makes contact with ovum’s plasma membrane the charges across the membrane reverse, thus repelling any incoming sperm (membrane polarization)
b) Slow Block (20-60 sec)= synthesis of a fertilization envelop due to Cortical Reaction
What are the difficulties w/ external fertilization? 1.Tonicity
With external fertilization, the egg is exposed to environments with varying solute concentrations.
- Saltwater: environment is high in solute and egg is full of solute (isotonic) -> egg can survive outside the body for some time until it is fertilized
- freshwater: the environment is low in solute whereas the egg is high in solute (difference in tonicity) -> water rushes inside egg causing it to burst prior to being fertilized. Therefore, eggs in freshwater must be fertilized quickly so it can form the fertilization envelope to prevent bursting
What are the difficulties w/ external fertilization? 2. Asynchrony
Asynchrony= releasing gametes into the environment at the wrong time resulting in ineffective fertilization
2 fixes that promote synchrony (ensure male/female release gametes @ same time)
a) Pheromones: chemical signal to release gametes
b) environmental cues: temp
What are the two types of Internal fertilization?
a) Direct Deposit: via copulatory organ (penis) and courting behaviours
b) Indirect Deposit: Male drops a spermatophore (capsule of sperm+nutrients to keep them functioning) into either the environment or into a female which ultimately decides to fertilize her eggs
What do we do with developing zygotes?
- Oviparity
- Ovoviviparity
- Viviparity and Matrotrophic
Oviparity: female lays eggs into the environment with little to embryo development (external brooding) which hatches outside of the mother (birds)
-deposit, cheap, offspring less likely to survive
Ovoviviparity: female allows the embryo to develop and hatch inside her reproductive tract (Internal brooding) which results in live births ex. pythons
-store
More familiar - Viviparity: live birth + constant nurturing via placenta during the development of the embryo ex. mammals. Another example found in sharks is Matrotrophic viviparity where young feeds off of uteral tissue (uteral milk)
-retain, fewer offspring, but stronger survival
What is Cleavage?
Mitosis continued without G phase (only S & M phase). Or the rapid cell division that takes place in animals after fertilization. Cleavage partitions the egg cytoplasm without additional cell growth resulting in an embryo (term for organism after initial mitotic division)
Order of the early stages of animal development (Starting @ fertilisation)
Fertilised egg -> cleavage -> morula (solid ball)-> blastula/blasocyst (hollow ball)-> gastrula (gastrulation= formation of 3 germ layers)
a) endoderm creates blastopore opening
b) dev’p archenteron/primitive gut
c) arrg’t of 3 germ layers)
- >late embryo (organogenesis)
What are the cells created though cleavage division called?
Blastomeres
Which organs/systems are formed from each germ layer?
Endoderm: digestive+respiratory+liver+pancreas
Mesoderm: dermis of skin+muscles+skeleton+circulatory+gonads+kidney
Ectoderm: Epidermis of skin+hair+glands of skin+nervous system (brain+spinal chord)
What is neurulation?
- a process that only occurs in chordates
- the formation of a dorsal hollow nerve chord (precursor of the spinal chord) from ectoderm tissue
What is metamorphosis?
The transition of the 3 germ layers to 3 tissue layers
Ectoderm: Epidermis (Skin), hair, skin glands, nervous system (brain & spinal chord)
Mesoderm: Dermis (skin), muscles, skeleton, gonads, kidneys
Endoderm: Digestive system, Respiratory system, liver, pancreas
