Animal Reproduction

• refers to the type of reproduction when the body of the parent grows buds, eventually falls off, grows on its own

  asexual reproduction
• this type of reproduction happens to animals that are stationary

  asexual reproduction
• asexual reproduction

  advantages: numerous offspring produced

  disadvantages: genetic variation does not occur; no change in characteristics
• this type of reproduction is the combination of the genetic material of 2 parents

  sexual reproduction
• this is the type of reproduction most humans and animals do

  sexual reproduction
• this type of reproduction commonly involves a male and female parent

  sexual reproduction
• egg's nucleus + sperm's nucles = zygote. this process is called fertilization

  zygote divides = embryo
• ASEXUAL REPRODUCTION

  •Organisms of the genus Hydra lives in freshwater lakes, ponds, and streams

  •Hydra develops a bud that is attached to the parent until it is fully formed.

  •Once it is fully formed, it detaches from its parent

  •The young hydra is now free to swim on its own until it find support and starts to reproduce
• SEXUAL REPRODUCTION

  •Hydras generally reproduce asexually during warm weather

  •Sexual reproduction usually occurs in autumn when the cold climate triggers the development of sperms and eggs

  •Sperm cells are released in the water.

  •Some reach the ovary of a nearby hydra, and one sperm fertilizes an egg

  •The fertilized egg or zygote then divides and grown into a ball of cells with a hard cover

  •The cover is an adaptation that protects the embryo until it develops into a new hydra
• ASEXUAL REPRODUCTION IN SPONGES

  •Able to reproduce asexually and sexually

  •Some sponges, the new individual buds from the parent.

  •In others, the parent sponge breaks into many fragments, and each fragments grows into a new sponge
• SEXUAL REPRODUCTION IN SPONGES

  •Sponge can also reproduce sexually.

  •After the male sponges release sperm cells into the water, water currents carry the sperm to female sponges where fertilization occurs

  •The fertilized eggs develop into larvae, which are then released

  •They swim in the ocean for a few days, after which, these larvae attach themselves to a solid surface and grow into new sponges
• •The jellyfish belong to phylum Cnidaria 

  •It has two different body forms during their life cycle

  -Polyp

  -Medusa
• MEDUSA AND POLYP STAGE OF JELLYFISH

  •The adult medusa releases either sperm or egg into the water where fertilization occurs

  •The resulting zygote develops into a blastula, which develops into a planula

  •The planula settles and attaches to the ocean floor, becoming a polyp

  •As the polyp grows, it forms into the medusa in the process called strobilation, wherein its reproductive structures are formed

  •Each of these stacks from the medusa then buds off and develops into a jellyfish.

  A) medusa

  B) polyp

  C) medusa

  D) planula

  E) planula

  F) polyp

  
• STARFISH

  •Fragmentation is another type of asexual reproduction in simple animals

  •In fragmentation, an organisms breaks into two or more parts, each of which may grow into separate individual

  •Starfish are animals that can be reproduce by fragmentation
• ASEXUAL REPRODUCTION IN FLATWORMS

  •Most living flatworms such as planaria are aquatic.

  •Flatworms can reproduce asexually by regeneration

  •When planaria regenerates, it is cut into two and each part regrows into a whole individual
• SEXUAL REPRODUCTION IF FLATWORMS

  •Most species are hermaphrodites.

  •Hermaphrodites are organisms having both male and female reproductive organs.

  •During mating, two flatworms exchange sperm so that the eggs of both flatworms are fertilized

  •A flatworm usually does not fertilize itself.
• annelids

  •animals: Earthworms and leeches

  •Most annelids reproduce sexually

  •Earthworms are hermaphrodites, but an individual worm cannot fertilize its own eggs

  •Two earthworms join head to tail, together they form mucus coat around the joined part of their bodies

  A) clitellum

  B) clitellum

  
• MOLLUSKS

  •Mollusks, such as land snails, are hermaphroditic

  •In most aquatic species, the sexes are distinct

  •Eggs are fertilized internally

  •Cephalopods, such as squids, have separate sexes

  •The male uses a specialized tentacle to transfer sperm from its cavity to the cavity of the female, where fertilization occurs

  •The female lays a mass of fertilized eggs encased in a gelatinous material

  •The female guards these eggs until they hatch
• ARTHROPODS

  •Spiders, insects, centipedes, scorpions, shrimps, crabs, and lobsters are all arthropods

  •The most numerous of these are the insects

  •The growth and development of insects usually involve metamorphosis, which is a process of transforming in a different shape and form
• INCOMPLETE METAMORPHOSIS IN INSECTS

  •Incomplete metamorphism

  •The young look like the adult, called nymphs

  •Nymphs gradually acquire adult structures such as wings and functional sex organs
• COMPLETE METAMORPHOSIS IN INSECTS

  •Insects, such as bees, moths, and beetles, undergo complete metamorphosis

  •These insects lay eggs that hatch into larvae that look different from the adults.

  •The larva changes into a pupa, after which, development into adult takes place.
• VERTEBRATES

  •Undergo sexual reproduction, which starts with fertilization.

  •Depending on the animal, fertilization may occur either outside or inside the female’s body
• EXTERNAL FERTILIZATION

  •Frogs undergo external fertilization

  •The female frog releases her eggs first

  •Then the male frog releases sperm over the eggs to fertilize them

  •The frogs leave the fertilized eggs to develop on their own way

  •In about two weeks, the eggs hatch into tadpoles

  •Some fishes and amphibians reproduce by external fertilization, in which the sperm fertilizes the egg outside the female’s body.

  •External fertilization must take place in a moist environment so that the delicate systems do not dry out

  •Fish and amphibians lay their eggs in water or in very moist areas.
• INTERNAL FERTILIZATION

  •The egg and sperm join inside the female’s body.

  •Reptiles, birds, mammals, and some fishes reproduce by internal fertilization

  •Reptiles lay their eggs on land

  •To prevent the eggs from drying out, the embryos within the reptile eggs are each surrounded by a watertight protective membrane called chorion

  •Chorion allows oxygen to enter the egg and carbon dioxide to leave

  •Within the chorion is another membrane called amnion, which encloses the embryo within a watery environment
• INTERNAL FERTILIZATION

  •Each egg is provided with a large amount of rich food for the embryo called yolk

  •The zygote develops within the egg, eventually taking the form of a miniature adult before it completely uses up the yolk

  •The egg then hatches and the young develops into an adult
• BIRD EGG

  •Amniotic eggs are also found in birds and mammals

  •The shell of a bird egg is hard enough to withstand the weight of the adult bird during incubation

  •The young that hatches from the eggs of most bird species are not able to survive unaided, since their development is still incomplete

  •The young bird are fed and nurtured by their parents, and they gradually grow into maturity
• MONOTREMES

  •Monotremes are the most primitive mammals that are oviparous and lay eggs like the reptiles

  •The living monotremes include the duck-billed platypus and echidna
• MARSUPIALS

  
  

  •Bear their young alive

  •The young of these mammals are nourished and protected by their mother

  •Marsupials, like kangaroo, are viviparous and bear their young alive

  •At the early stage of its development , the young crawls into its mother’s pouch called marsupium.
• PLACENTAL MAMMALS

  •Placental mammals give birth to their young alive

  •After birth, most placental mammals provide their young with a period of care

  •The duration of this parental care varies among different species

  •The young of monkeys and humans are helpless at birth and for quite some time

  •These infants depend on their mother for food and protection

  •They spend several years growing up before they are able to live on their own