Reproduction

Goal of reproduction?

Produce another generation

—if species survives survives (does not go extinct) mode of reproduction can be deemed sufficient 

Parthenogenesis (what and who?)

Asexual reproduction, where an egg (ovum) develops into a new individual without fertilization

—Found in some fish (trinidad guppies), some lizards (whiptail lizards) a python from SE Asia and occasionally in turkeys, komado dragons and boas

Hermaphroditism (what and who?)

Individuals have both sets of sex organs

Type 1: Simultaneous: both sets present but don’t function at the same time, so usually do not self fertilize (e.g, Hamlet fish) self-fertilize

Type 2:Sequential: born with one sex, then switch to the other

• Type a: Protandry: first male>then female (e.g, clownfish)

• Type b: Protogyny: first female> then male (e.,g wrasses)

Simultaneous Hermaphroditism

Both sets present but don’t function at the same time, so usually do not self fertilize (e.g, Hamlet fish) self-fertilize

Sequential Hermaphroditism

Sequential: born with one sex, then switch to the other

Type a: Protandry: first male>then female (e.g, clownfish)

Type b: Protogyny: first female> then male (e.,g wrasses)

Sequential Hermaphroditism: Protandry

first male>then female (e.g, clownfish)

Sequential Hermaphroditism: Protogyny

first female> then male (e.,g wrasses)

Sex Determination Types?

Genetic Sex Determination (GSD): sex of offspring determined by chromosomes, in birds/mammals

Temperature Sex Determination (TSD): Temperature determines the sex of offspring (alligators,turtles,fish)

What are the reproductive strategies of vertebrates?

1. R-Selected: tons of offspring with a low survival rate

   • fish, amphibians ,small rodents

2. K-Selected: few offspring witha high survival rate

   • long-lived species: primates ,whales,seabirds

External Fertilization

• Ova and sperm combine OUTSIDE of the female body

• fish and amphibians

• adaptations to increase # of ova fertilized

  • large # of games especially ova

  • synchronized gamete release

  • behaviors to bring sexes in close contact (e.g, amplexus)

amplexus

the mating position of anurans, in which the male clasps the female about the back (close contact breeding behavior)

Internal Fertilization

• sperm and ova combine WITHIN the body of the female

• All birds, mammals, reptiles, chondrichthyes, and some salamanders

• Copalatory structures

  • penis (or intromitent organ)

  • cloacal protuberance (birds)

  • claspers/ modified pelvic fin (sharks and rays)

Gamete Numbers

Primarily refers to ova

1. Few released (cycle fashion)> behavioral adaption to increase offspring survival

2. Many released (simultaneously)> high mortality rate

Parental Care in mammals and birds

HIGH

Parental care in fish

LOW

Some snakes _____ egg

incubate

Species with high amounts of offspring _________

little parental care

Species with low amounts of offspring _________

high parental care

Oviparous

Embryo develops in structure OUTSIDE of female body (EGG)

-common in fish, amphibians, some reptiles, all birds, monotreme mammals

Ovovivparous

Female produces egg but retains within reproductive tract (egg hatches INSIDE female then EXITS ALIVE)

-snakes,sharks

Viviparous

Embryo developed in female’s body (pregnancy) (placenta) (BORN ALIVE)

-all mammals except monotremes, some amphibians

Pair Bonding

Behavioral attachment between sexes, important to reproductive processes

1. monogamy

2. polygamy

3. promiscuous

Monogamy

1 m + 1 f bonded at lease through breeding season

• can sometimes last for life (swans)

• Historically thought most popular BUT ISN’T (pretty uncommon except some birds)

Polygamy

Multiple bonds formed at one time or sequentially

1. Polyandry (1 female + multiple males)

   • pretty uncommon and rare

2. Polygyny (1 male + multiple females)

   • more common

   • examples in all groups

Polyandry

type of polygamy

(1 female + multiple males)

pretty uncommon and rare

Polygyny

(1 male + multiple females)

more common

examples in all groups

Promiscuity

No real pair bonds formed, multiple partners

• come together only to shed gametes

• many fish, reptiles and mammals

• may be most common especially when competition and sperm storage

Breeding Season

• Most vertebrates have distinct seasons

  • Fish (spring), Deer (fall), etc.

  • Humans, mice, etc., anytime

• Natural selection determines when breeding occurs

____________ determines when breeding season occurs

Natural selection

Breeding Season Proximate Factors

Factors that let organism know breeding season approaches

• Photoperiod: number of daylight hours in 24 hour period

• Temperature: especially of water

• Tidal cycles

• Rainfall: when sunlight does not vary, monsoon (or rainy season) sets of reproduction

Breeding Season: Ultimate Factors

Factors that cause a species to breed at time of year to increase

success

• Food: availability when offspring are born

• Nesting/breeding sites

• Climate

Reproduction - Fish

• Much sexual dimorphism: color, forehead crests, hooked jaws, size, etc.

• Chondricthyes: most have internal fertilization

• Osteichthyes: most have external fertilization

• Some have elaborate courtship dance that identifies mate and leads them through nest (where eggs then sperm deposited)

Reproduction - Amphibians

• Sexual dimorphism present – several sexual characters develop during breeding season (mental glands, nuptial crests, etc.)

• Varied forms:

  • eggs deposited in water (where larvae develop)

  • eggs deposited on land (then larvae develop in water)

  • eggs and young terrestrial

• Anurans: most external fertilization: male grasps female (amplexus) to stimulate egg expulsion (coordinates spermrelease)

• Caecilians: internal fertilization (males have phallodeum), most are viviparous

• Salamanders: most internal fertilization via spermatophore (packet of sperm): elaborate courtship dance leads female to spermatophore

Reproduction - Reptiles 

Amniotic egg: less dependence on water

• Most are oviparous with internal fertilization

• Courtship often involves stereotyped displays (head-bobs, dewlap extension, etc.)

• Breeding aggregations can be large in some species

Reproduction - Birds

• Sexual dimorphism prevalent

• Courtship involves species-specific songs,

postural displays, and some elaborate

dances

• Monogamy more common than in other

vertebrate groups, but not universal

Reproduction - Mammals

• Most mammals have internal fertilization and are viviparous

• Sexual dimorphism can exist: many times related to body size,

also male cervids (deer, elk, etc.) grow antlers

• Courtship during mating season involves calls, male-male

competition, and other displays