Asexual & Sexual REPRODUCTION

ASEXUAL REPRODUCTION Requires 1 parent Requires 1 parent Offspring genetically identical to parent (clones = exact copies) Offspring genetically identical to parent (clones = exact copies)

Advantages No need for a mate No need for a mate Takes less time and energy Takes less time and energy Reliable = fewer steps Reliable = fewer steps Produces large numbers of offspring very quickly Produces large numbers of offspring very quickly In stable environments with very little change, well- adapted organisms can spread & colonize quickly In stable environments with very little change, well- adapted organisms can spread & colonize quickly Tends to require less parental care Tends to require less parental care Disadvantages Very little genetic variation in a population Very little genetic variation in a population Harmful mutation in parent will be passed on to all offspring Harmful mutation in parent will be passed on to all offspring Entire population of genetically-identical organisms can go extinct if there is a change in the environment Entire population of genetically-identical organisms can go extinct if there is a change in the environment ASEXUAL REPRODUCTION

PROKARYOTES rocess of BINARY FISSION- “one cell into two” Process of BINARY FISSION- “one cell into two” ASEXUAL REPRODUCTION

UNICELLULAR EUKARYOTES Most protists and fungi like yeast Most protists and fungi like yeast Process of MITOSIS: division of nucleus & then CYTOKENESIS: division of cell Process of MITOSIS: division of nucleus & then CYTOKENESIS: division of cell ASEXUAL REPRODUCTION

MULTICELLULAR EUKARYOTES: ANIMALS ASEXUAL REPRODUCTION REGENERATION: Replacement of all or part of an organism. Examples: planarians & starfish REGENERATION: Replacement of all or part of an organism. Examples: planarians & starfish BUDDING: Growth of a new organism off of another. Examples: hydra & corals BUDDING: Growth of a new organism off of another. Examples: hydra & corals

ASEXUAL REPRODUCTION MULTICELLULAR EUKARYOTES: ANIMALS PARTHOGENESIS: Production of offspring by females without fertilization by a male PARTHOGENESIS: Production of offspring by females without fertilization by a male – All offspring are female – Occurs naturally in some worms, insects & reptiles

VEGETATIVE PROPAGATION: Production of a new plant from an existing plant or part of a plant VEGETATIVE PROPAGATION: Production of a new plant from an existing plant or part of a plant ASEXUAL REPRODUCTION MULTICELLULAR EUKARYOTES: PLANTS grafts runners cuttings tubers buds bulbs

SEXUAL REPRODUCTION Requires 2 parents Requires 2 parents Fusion of gametes from both parents creates a zygote Fusion of gametes from both parents creates a zygote GAMETE: specialized reproductive cell produced through MEIOSIS (special type of cell division) GAMETE: specialized reproductive cell produced through MEIOSIS (special type of cell division) Offspring have unique combination of DNA from both parents Offspring have unique combination of DNA from both parents Increases genetic variability among offspring Increases genetic variability among offspring SEXUAL REPRODUCTION

5 Advantages Each offspring is unique Each offspring is unique Allows for more variation within a species Allows for more variation within a species Population able to adapt to changes in the environment (recall natural selection) Population able to adapt to changes in the environment (recall natural selection) Mutations are less likely to affect a single organism negatively Mutations are less likely to affect a single organism negatively Disadvantages Time & energy to find a mate Time & energy to find a mate Fewer offspring Fewer offspring More time to develop offspring More time to develop offspring Tends to require more parental care Tends to require more parental care SEXUAL REPRODUCTION

CONJUGATION: Temporary union of two single cells with at least one of them receiving genetic material from the other SIMPLEST FORM OF SEXUAL REPRODUCTION Protista: paramecia Fungi: molds Protista: paramecia Fungi: molds SEXUAL REPRODUCTION SIMPLE ORGANISMS

(+) OR (-) GAMETES: In fungi, like mushrooms, gametes are identified as plus(+) or minus(-) when male/female cannot be identified SEXUAL REPRODUCTION NO DISTINCTION OF SEXES

DISTINCTION OF SEXES GAMETES are identified as distinctly MALE or FEMALE GAMETES are identified as distinctly MALE or FEMALE – Due to presence of separate sex chromosome Y or X HERMAPHRODITIC organisms HERMAPHRODITIC organisms – Male/female gametes produced within same organism flower pine earthworms SEXUAL REPRODUCTION

SEXUAL REPRODUCTION in Flowering Plants Pollen is produced in the anthers (male organs). Pollination occurs when pollen is transferred from the anthers to the stigma (female organs) by wind or by animals. If the stigma is receptive to a pollen grain, the pollen produces a pollen tube, which grows through the female tissue to the egg where fertilization takes place by the sperm nucleus.

DIFFERENTIATION OF SEXES Gametes are produced in separate organisms Gametes are produced in separate organisms – Most advanced form of sexual reproduction MALE FEMALE SPERMATOZOA OVA (EGG) SEXUAL REPRODUCTION

EXTERNAL FERTILIZATION External fertilization usually requires a medium such as water which the sperm can use to swim towards the eggs. External fertilization usually requires a medium such as water which the sperm can use to swim towards the eggs. External fertilization usually occur in aquatic invertebrates, fish and amphibians. External fertilization usually occur in aquatic invertebrates, fish and amphibians. SEXUAL REPRODUCTION

INTERNAL FERTILIZATION Fertilization occurs within the female Fertilization occurs within the female Internal fertilization occurs in mammals, insects, birds, reptiles Internal fertilization occurs in mammals, insects, birds, reptiles – Mammals (gorillas, lions, elephants, rats, zebras, and dolphins have live births) – Insects, birds, reptiles lay eggs SEXUAL REPRODUCTION