Reproductive strategies are structural, functional and behavioural adaptations that improve the chances offertilization and/or increase the survival rate of
Asexual Reproduction Requires only one parent Offspring have 100% the same chromosomes as the parent. In other words, the offspring are exact “clones” of the parent. Mitosis
Types of Asexual Reproduction There are several different types of asexual reproduction they are: Binary Fission Budding Fragmentation Regeneration Parthenogenesis
Binary Fission Binary Fission Occurs in: Bacteria Protists Binary fission is a formof asexual reproduction where every organelle is copied and theorganism divides in two. 6
Budding Hydra Budding is a means of asexual reproduction whereby a new individual develops from an outgrowth of a parent, splits off, and lives independently.
Fragmentation Fragmentation is a means of asexual reproduction whereby a single parent breaks into parts that regenerate into whole new individuals.Starfish Planarians 8
Regeneration Regeneration occurs when a body part has broken off and the organism grows a new one. http://www.youtube.com/watch?v=f7cXeWxxfD4 9
Parthenogenesis This type of reproduction involves the development of an egg that has not been fertilized into an individual. Animals like most kinds of wasps, bees, and ants that have no sex chromosomes reproduce by this process. Some reptiles and fish are also capable of reproducing in this manner.
Sexual Reproduction Requires two parents that each share ½ of the genetic information. Offspring share the characteristics of each parent. Meiosis to create sex cells
Sexual Reproduction All the members of the Animal Kingdom Fish Mammals Amphibians Birds Reptiles Insects Crustaceans
Sexual Reproduction in plants Plant Kingdom Flowers are the reproductive organs of plants. Male flower Female flower Some flowers have both male and female reproductive organs on the same flower.
Sexual Reproduction Happens 2 ways Internally (inside) The egg is fertilized by sperm inside the female Mammals, birds, reptiles, insects, spiders Externally (outside) The egg is fertilized by sperm outside the female The female lays the eggs and then the male fertilizes them. Fish and some amphibians Plants and fungi (pollen and spores) 16
Summary Asexual Reproduction Sexual Reproduction No genetic differences Random gamete formation and combination allows genetic variationSimple and easy – no need Must find a suitable partner to find a mate – time and effort Little energy expended More energy required Good strategy when Good strategy whenenvironmental conditions environmental conditions are favourable are variable
External versus Internal fertilisation Male gametes are small, fragile and prone todehydration. Aquatic organisms are able to dispersetheir gametes in the water around them. Terrestrial organisms require alternative methods to ensure viable sperm is able to fertilize the egg.
Broadcast Spawning: Reef fish that gathertogether and release their eggs and spermsimultaneously into the water – these eggs aretermed ‘pelagic’, or free-floating. (eg.Boxfish, abalone and coral)
Demersal Spawning:Fish that lay eggs togetherin a type of ‘nest’ (a hollowin the sand or a crevice inrocks) which are thenfertilised by the males aredemersal spawners. Theyproduce larger and fewereggs than broadcastspawners, because energyis needed to guard andclean the eggs. (eg.Anenome fish)
MonogamyMore than 90% of bird species are monogamous, that is, they form pairsfor one or more breeding seasons. Eg. Eagles, albatross and brolgas.These species are more likely to have altricial development (requiresignificant parental care).
PolygamyPolygyny (one Polyandry (onemale, many females) female, many males)
Promiscuous – males and females in a social groupengage in multiple and indiscriminate mating.
Fast versus slow Fast reproductive strategies are known as R-strategies Slow Reproductive strategies are called the K-strategy
R-selection (Quick and many Eg. Mice andrabbits)
K-selection (slow and fewEg. Elephants, whales, humans)
Slow (K) vs Fast (r) Large body size • Small body size Long life span • Short life span Take a long time to • Sexually mature very sexually mature quickly (weeks to months)
Slow (K) vs Fast (r) Typically carry 1-2 • Carry/hatch many young young • Must care for themselves Protect and nurture at an early age their young • Low Survivorship of High survivorship (type young (many die) – type 1) of species over time. 3
Eggs or live born young? Oviparity – eggs released by the mother so embryos develop outside mother’s body with nutrients for the embryo coming from the egg yolk Viviparity – embryos develop within the mother’s body and are born as miniature copies of the adult. Nutrition of the developing embryo within the mother occurs in different ways.
Oviparity Oviparous animals lay hard- shelled eggs that act as a ‘pond’ for the developing embryo. The yolk of the egg acts as a source of nutrients. The size of the newly hatched young is determined by the yolk supply in the egg – the larger the yolk, the larger the young.
Vivaparity – Live birth Placental mammals (Eg. humans, cats, dogs, sheep and cows). Viviparity increases the chance of survival by protecting the young within a female’s body rather than leaving them exposed to predators