Types of Sexual Reproduction

Vocabulary Conjugation, hermaphrodite Stamen, filament, anther, pollen Pistil, stigma, style, ovary, petals, petals, sepals, pollination external fertilization, internal fertilization

Conjugation Conjugation occurs when two unicellular organisms transfer or exchange some of their genetic material. Some bacteria and certain protists like Paramecium Example: bacteria like E.coli one cell copies an extra piece of DNA (called a plasmid) and donates the plasmid copy to another cell  

Autogamy – Self Fertilization “Auto” means “self” Autogamy means an organism can fertilize itself Hermaphrodites are organisms that produce both male and female sex cells within the same individual. Hermaphrodites occur in plants and some animals that are attached to one location and/or rarely come in contact with other individuals of their species. Eg many aquatic organisms (sponges and barnacles), Earthworms, flowers Although autogamy is similar to asexual reproduction, in that there is no input of genetic diversity from a partner, the recombination of chromosomes from the male and female gametes results in offspring with slightly altered genetic information, which can therefore look phenotypically different from their parents. Most plants and earthworms reproduce by autogamy. It is sometimes possible for hermaphrodites to reproduce with other hermaphrodites. In this case, genetic diversity does increase within the population.

Compare Autogamy to Asexual Reproduction It is possible for hermaphrodites to reproduce with other hermaphrodites. In this case, genetic diversity does increase within the population.

Compare Autogamy to Asexual Reproduction Similar: No partner, No input of genetic diversity. But: the recombination of chromosomes from the male and female gametes results in slightly genetically different offspring It is possible for hermaphrodites to reproduce with other hermaphrodites. In this case, genetic diversity does increase within the population.

Allogamy – Cross Fertilization Allogamy is the fertilization of an egg from one individual with the sperm of another . Occurs in most complex animals and some plants Eg. Conifers such as pine and fir trees have separate male and female cones on the same plant. Some species have separate male and female flowers on the same plant Poplar trees have separate sexes on separate plants.

Fertilization – Fusion of Nuclei Fertilization is the process in which the nuclei of the male and female gametes fuse together to produce a single cell called a zygote. Sperm cells have long tails “flagella”. Egg cells are much bigger and lack flagella. What does the presence or absence of flagella say about the cells motility?

External Fertilization gametes meet outside of the parents The female deposits unfertilized eggs and males release sperm over the eggs. Common in fish and amphibians https://www.youtube.com/watc h?v=q50Yphp1gzI fertilization (the exceptions are aquatic mammals, sharks, and some other special types of fish). External fertilization usually occurs among organisms living in aquatic environments. Land animals generally have specialized organs for internal fertilization.

Advantages of External Fertilization Energy Efficient: Requires very little effort as the sperm and egg can randomly meet Easier to find mates as the gametes released can drift (wind, water etc). Low Parental Burden: Female does not have to physically carry the developing offspring Many Offspring, More genetic variation No specialized structures required to have gametes meet

Disadvantages of External Fertilization Egg, zygotes, young susceptible to environment (drying out) and predation. No guarantee that eggs will be fertilized. Large numbers of eggs need to be produced to ensure some survival.

Internal Fertilization

Internal Fertilization Gametes meet inside female’s body Requires specialized structures to ensure meeting of gametes Occurs in mammals, reptiles, birds, and some types of fish  All land dwellers need to fertilize this way because sperm still prefer swimming Need specialized structures. Penis

Advantages of Internal Fertilization Better chance gametes will meet, greater change of fertilization Controlled environment: wet environment, temperature regulation, protection from predators More stringent mate selection Video of sneaky fish: https://www.youtube.com/watch?v=RzTy0fAwBFk

Disadvantages of Internal Fertilization Mating can be risky, partners vulnerable during intimate contact Complex courtship and mating behaviours https://www.youtube.com/watch?v=W7QZn wKqopo Limited amount of offspring being produced at any given time.  Parents must care for young through out gestation Specialized structures are required to ensure the meeting of gametes

Bower Bird Bower Bird video https://www.youtube.com/watch?v=GPbWJPsBPdA

Puffer Fish https://www.youtube.com/watch?v=VQr8xDk_UaY

Internal and External Fertilization Name an organism for each method How is internal fertilization an advantage over external? Why do you think organisms that reproduce using external fertilization release a large number of eggs and sperm?

Check your understanding How does the process of fertilization occur? What is needed for fertilization to occur? Describe the different forms of fertilization and give an example of an organism that uses them.

Advantages of Asexual Reproduction No partner necessary (energy efficient) Fast – each organism can produce many offspring  rapid population growth Offspring mature quickly Offspring are already adapted to environment All advantages help an organism become establish de quickly and successfully in the conditions provided by its environment. But what if conditions change? many Food crops depend on asexual reproduction – new plants can be grown quicly and in large number when they are produced this way. The plants that come from themhave predictable qualities that consumers expaect. But what if there is o rain for a long time. Or if the plats are invaded by a disease? Because all plants are genetically identical, they will all respond the same way --. Become diseased and possible die.

Disadvantages of Asexual Reproduction Less genetic variation - all offspring are clones and therefore all susceptible to disease Harder for species to adapt to environment Slows down evolution All advantages help an organism become establish de quickly and successfully in the conditions provided by its environment. But what if conditions change? many Food crops depend on asexual reproduction – new plants

Why Sex? Possible Benefits: Genetic variation: offspring’s DNA is different and therefore may be better prepared for any changes in the environment Any disease that affects some of the offspring will not affect all of them  some will still be able to survive and reproduce Variation in DNA leads to evolution Why would organisms need to evolve? Is change good? Environment changes, organisms need to adapt to changing environment.

Why Sex? Disadvantages Time and Energy costly –finding a mate, courtship is time and resource costly Usually fewer offspring produced Slower – gestation (development of fetus inside womb) and longer time for offspring to mature More energy investment into raising young Time and Energy costly –finding a mate, courtship is time and resource costly (may expose individuals to predators, disease, or harsh conditions. This can delay reproduction and organism’s ability to become established in its environment. Fewer offspring also then takes longer to establish in environment Usually sacrifices fitness of one sex to the other. Slower Why would organisms need to evolve? Is change good? Environment changes, organisms need to adapt to changing environment. Bower bird nest Jasper story Elephant gestation 18-22 months

Strange Animal Behaviour https://www.youtube.com/watch?v=R6R-Hm0enGg HW: Read 83-84, 86, HW: Answer CYU p87 #2,3,5,8-11,14

Compare Asexual and Sexual Reproduction Feature Asexual Sexual Number of parents Number of offspring Variety of offspring Speed of reproduction Timing Energy cost

Feature Asexual Reproduction Sexual Reproduction Number of parents One two Number of offspring Usually many Usually few Variety of offspring Genetically identical Genetically different Speed of reproduction Usually fast Usually slow Timing Anytime, once mature Once mature, only when a mate is available