propagation of the species, so that generations after generations can be in existence
Types of reproduction:
Which occur in animals?
Which one is used?
asexual and sexual
both, one or none
Asexual reproduction: __
propagation of a new offspring by mitosis; one parent (monotonous reproduction
Result: produces a genetically identical copy of itself, a clone; no genetic variation
What are the kinds of asexual reproduction?
budding: outgrowths of existing individuals; a group of cells grow on the body and, through mitosis, grows to become a new individual, which then detaches
separation individuals of approximately the same size.
specialized diploid cells are partitioned (set aside) somewhere in the parent--> released into the environment--> divide mitotically to form a new individual
breaking into pieces, where each piece regenerates its missing part by regeneration
a new haploid individual forms from an unfertilized egg
Individuals are sterile; some remain haploid; others turn diploid
Example: bees [worker]
Advantages of asexual reproduction.
not finding mate; if species is scarce, they don't worry
more offspring at a faster rate
if the gene pool is favorable, it passes on, assuring persistence
Disadvantages of asexual reproduction.
If there is a bad gene, it is transferred
lack of diversity
unfavorable genes perpetuate (deleterious)
What is sexual reproduction?
two parents each produce haploid gametes, fuse in fertilization, and form a diploid zygote
- creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote
Gametes form by __--> fertilization--> zygote--> grows by __.
Advantages of sexual reproducion?
genetic variation via recombination and independent assortment
- every offspring can be genetically differetn from every other offspring
- recombination does a good job hiding deleterious genes (recessive genes)
Changing environments are accommodated through adaptations
Disadvantages of sexual reproduction.
finding a mate
takes a longer time
individuals contain both male and female gonads and other reproductive structures
They reproduce sexually, but do not self-fertilize [eggs can be fertilized by own sperm]
Example: earthworm and sea slugs (sea slugs produce own sperm and eggs; in a few weeks, new individuals hatch from fertilized eggs)
Some species undergo __. Explain it.
female can change into a male and vice versa via environmental cues
What does all fertilization require?
mediated by environmental cues (pheromones and chemical attractants (maybe))
courtship and mating behaviors
What are the two types of fertilization in sexual reproduction?
external and internal
1) union of gametes outside body:- male and female release gametes into environment; has to be moist environment
2) accompanied by large #s of gametes being spread to ensure some gametes will be successful in finding other gametes: - the further the distance away the male is from the female, the more eggs the female sheds (only females; sperm is always in large #s)
3) Attraction to eggs: - pheromones and chemical attractants
What are phermones and chemical attractants?
pheromones: hormones that are released that help lure/ affect behavior of opposite sex
chemical attractants: materials released by the outer coats of eggs/ some are highly specias specific/ characteristic of external because internal isn't as important
Why are courtship behavior and mating behaviors important?
important for proper union
1) The sperm are deposited inside female--> gametes fuse inside body
2) Requires some behavioral interactions- a copulatory organ--> male needs some way to place sperm inside body
What is special about internal fertilization?
development can be outside or inside body
There are three types of organisms depending on whether development is inside or outside the body.
Internal fertilization and the modes of development.
1) egg-laying animals
2) little/ no development occurs in mom
3) before egg is shed, its covered with protective casing (may be hard shell or leathery)
Examples: most fish, amphibians, and reptiles; all birds; most insects; etc.
1) internal fertilization and internal development where the embryo and the mom are connected by a placenta formed between the mom and baby
2) Mom's blood vessels in close proximity to th ebaby's blood vessels, enabling nourishing of the baby, waste being taken away, etc. by the placenta
Examples: all placental mammals, except marsupials.
1) internal fertilization, but the embryos are carried in body, either the male or female body
2) no interaction between the parent body and embryo
3) embryo grows in self-sufficient manner, not relying on parent for anything but a place during its growth
4) appears as live birth because the casing breaks open and allows release of offspring
Examples: marsupials and frogs
Explain reproductive cycles.
1) most animals exhibit reproductive cycles related to changing seasons
2) Reproductive cycles are controlled by hormones and environmental cues.
3) Estrous vs. Menstrual
Explain the estrous reproductive cycle.
Occurs in most female placental mammals, except humans.
It is often referred to as "heat" where the female is reproductively receptive to the male; corresponds to ovulation cycle in female where she is receptive to intercourse with the male
Humans and males are exceptions
Any organism that reproduces sexually must have:
gonads (gametes/ sex hormones)
accessory structures (ducts/ glands)
pair of primary reproductive organs
play role in nourishment, transport, protection of fertilized egg and developing embryo