reproduction

I.Characteristics of sexual reproduction

sexual reproduction involves the meeting of two cells called ? one from each parent

gametes

I.Characteristics of sexual reproduction

Male gametes are ? (sperm) and female gametes are ? (eggs; oocytes)

• spermatozoa

• ova

I.Characteristics of sexual reproduction

Fertilization –

 the point at which a sperm successfully penetrates the egg – can occur either within the female (internal) or in the surrounding environment (external)

external fertilization

aquatic animals (frogs, toads, bony fish, and marine invertebrates) usually release their gametes into the water known as ?

spawning

internal fertilization

Internal fertilization typically involves a ? inserted into the female reproductive tract (penis in mammals, phallodeum in caecilians, phallus in waterbirds), but not every species has such a structure:

male reproductive organ

internal fertilization - male reproductive organ

Some species of salamanders drop a packet of sperm (?) after elaborate courtship, which the female picks up with her cloaca

spermatophore

number of eggs, energy, and protein provision

All birds, most reptiles, and terrestrial insects lay self-contained eggs (called ? from the Greek word meaning closed)

cleidoic

number of eggs, energy, and protein provision

In mammals, egg-laying only occurs in ? (platypus and echidna)

monotremes

Yolk consists of the nutrients and enzymes necessary for development of fertilized eggs, its distribution differs between species:

? eggs have evenly distributes yolk (mammals)

isolecithal

Yolk consists of the nutrients and enzymes necessary for development of fertilized eggs, its distribution differs between species:

? eggs have concentrated on one side, opposite the embry (amphibians and birds)

teleolecithal

Yolk consists of the nutrients and enzymes necessary for development of fertilized eggs, its distribution differs between species:

? eggs have yolk concentrated in the center of the egg (insects

centrolecithal

Eggs also fall into four categories based on the amount of yolk they contain:

alecithal

eggs have no yolk (placental mammals)

Eggs also fall into four categories based on the amount of yolk they contain:

microlecithal

eggs contain small amounts of yolk (marsupials and echinoderms)

Eggs also fall into four categories based on the amount of yolk they contain:

mesolecithal

eggs contain intermediate amounts of yolk (most fish and amphibians, enabling embryos to hatch at later stages of development)

Eggs also fall into four categories based on the amount of yolk they contain:

macrolecithal

eggs have a large amount of yolk ( insects, cartilaginous and bony fish, reptiles and birds, enabling the young to hatch even later in development

Species that hatch as well-developed, mobile young with eyes open, covered with down/fur, and able to thermoregulate are called

precocial

Species that hatch with their eyes closed, incapable of moving around, and unable to thermoregulate are known as

altricial

Some animals must accumulate sufficient reserves of these lipids and proteins for egg formation and laying, termed

capital breeders

In contrast, small animals tend to be

income breeders, reliant on continual food intake supply protein/lipids to the eggs

what is the process of depositing nutrients (mainly vitellogenin) into the oocytes that will develop into the yolky eggs

income breeders

There are three main egg-laying strategies:

oviparous

animals release eggs in which there has been little or embryonic development

There are three main egg-laying strategies:

ovoviparious

animals retain their fertilized eggs and give the developing young protection, although the nutrietns needed are contained within the eggs

There are three main egg-laying strategies:

viviparous

(live bearing) animals provide the daily nutritional requirements of the embryo throughout the development

there are three main egg laying strategies

-Placental (eutherian) mammals develop a characteristic ? which forms a connection between mother and fetus, providing nutrients, oxygen, and hormones while removing metabolic wastes and carbon dioxide

placenta

Most animals reproduce more than once in their lifetime (=?)

iteroparity

Some animals have a once-in-a-lifetime breeding event (=?) and are characterized by the extent to which their body becomes dedicated to reproduction

semelparity

fluctuations in rainfall and changing photoperiod (alternating melatonin secretion) act as cues for ? ?

seasonal breeding

variations in food intake and quality can affect reproductive success (?)

carryover

??? occurs in most species if not all

genetic sex determination

genetic sex determination

the most common system of genetic sex determination is? ? ? genetic males are heterogametic (XY) and genetic females are homogametic (XX)

XY/XX sex chromosome system

several other systems of genetic sex determination occur

Birds, some fish, some reptiles (all snakes and some turtles and lizards), and some amphibians (newts and salamanders) have a ? ? ? ? where the male is homogametic (ZZ) and the female is a heterogametic (ZW)

ZW sex chromosome system

? ? is the development of gonadal, neural, and endocrine tissues to determine an animal’s phenotypic sex

sexual differentiation

gonadal sex determination

In placental mammals and marsupials, a delay of up to several weeks occurs before the sex-regulating region of the Y chromosome (? ?) triggers masculinization

SRY region

gonadal sex determination

however the release of ? from the developing testes results in differentiation of the characteristic features of the male reproductive tract and external genitalia

testosterone

the genetic sex and phenotypic sex are usually identical but differences can arise

if the animal lacks ? ? the masculinizing effects of testosterone

androgen receptors

temperature dependent sex determination

studies have identified ? ? of development during which the incubation temperature can change gonadal development

thermosensitive period

there are two types to the thermosensitive period:

pattern 1

animals tend to to have a single temperature transition zone with males on one side and females on the other side of the transition temperature, with a mixture in between

there are two patterns to the thermosensitive period

pattern 2

animals have two temperature transition zones with males in the intermediate temp and females at both extremes

what are responsible for the differentiation of ovaries

estrogens

what enzyme converts testosterone, the main ? (male sex hormone) to estradiol

-aromatase

- androgen

some animals produce both male and female gametes:

hermaphrodites

animals that produce both male and female gametes

D.Some animals produce both male and female gametes

? ? in which an ovotestis produces both male and female gametes simultaneously

simultaneous hermaphroditism

simultaneous hermaphroditism:

these could in theory self fertilize but usually exchange gametes instead

mutual insemination

? ? in which the gonads initially form one type of gamete but then change to the other type

sequential hermaphroditism

sequential hermaphroditism

protandry -

male formed first

sequential hermaphrotditism

protogyny

female formed first (sheephead fish)

vertebrate reproductive systems and gametogenesis

gametogenesis

the process of developing male and female gametes

vertebrate male reproductive systems

spermatogenesis

is the process of sperm production from male gonads

vertebrate male reproductive systems

the testes are composed of seminiferous tubules with rings of ? ? which support the development of the ?

-Sertoli cells

-spermatogonia

? undergo mitosis to form ? ?

-spermatogonia

-primary spermatocytes

Primary spermatocytes then undergo meiosis I to form ? ? and then meiosis to form ?

-secondary spermacytes

-spermatids

spermatids then go through the process of ? to become motile ?

-spermiogenesis

-spermatozoa

the transformation of spermatids into spermatozoa is called? which involves

-Reducing the amount of cytoplasm

-Condensing the chromosomes into the head

-Adding a motile tail

sperimiogenesis

spermatozoa are made up of several characteristics features

-the ? - a cap on the head important in penetrating the ovum during fertilization

acrosome

capacitation

is the process of increasing the fluidity of the acrosomal membrane resulting in higher permeability to Ca ions which increases sperm motility and their capacity to bind to an ovum

Hormones of the hypothalamic-pituitary axis are involved in male reproductive function:

gonadotropin releasing hormone (GnRH) from the hypothalamus stimulates release of ? ? and ? ? ? from the anterior pituitary

• lutenizing hormone (LH)

• follicle stimulating hormone (FSH)

? what triggers Leydig cells in the testes to secrete testosterone

LH

? and testosterone trigger Sertoli cells of seminiferous tubules to promote ?

- FSH

-spermatogenesis

large increases in testosterone at puberty drive development of ? ? ? which occur annually or seasonally in seasonal breeders

secondary sexual characteristics

vertebrate female reproductive systems

most vertebrates have paired ? and two ?

-ovaries

-oviducts

vertebrate female reproductive systems

Often, the oviduct is just a conduit, but in some animal groups, specialized segments add outer layers or casings to the developing egg (elasmobranchs, birds, reptiles, and insects laying cleidoic eggs)

in birds the ? adds albumin, the ? adds egg membranes, and the ? ? adds the calcium rich shell and outer pigments

-magnum

-isthmus

-shell gland

vertebrate female reproductive systems:

in viviparous animals, the oviducts fuse to form a specialized region to hold the developing embryo (? in mammals)

uterus

vertebrate female reproductive systems:

uterus of mammals has two layers: a muscular ? and a highly vascularized ? where the embryo implant

-myometrium

-endometrium

vertebrate female reproductive systems:

?/? is the process of forming follicles/eggs (ova) from the female ovaries

folluculogenesis/oogenesis

? are formed by mitosis from the PRIMORDIAL GERM CELL prior to birth

oogonium

before or soon after birth oogonium enter meiosis I to form ? ?

primordial follicle , which contains primary oocyte, which then enters prophase

hormonal control of folliculogenesis/ovulation:

? stimulates release of FSH and from pituitary , which stimulates follicular growth

GnRH

? stimulates secretions of androgens ; ? converts those to estrogens, stimulating ? ?

-LH

-aromatase

-cell proliferation