Asexual & Sexual REPRODUCTION

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

ASEXUAL REPRODUCTION Advantages Disadvantages No need for a mate Takes less time and energy Reliable = fewer steps Produces large numbers of offspring very quickly In stable environments with very little change, well-adapted organisms can spread & colonize quickly Tends to require less parental care Very little genetic variation in a population 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

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

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

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

MULTICELLULAR EUKARYOTES: ANIMALS ASEXUAL REPRODUCTION MULTICELLULAR EUKARYOTES: ANIMALS PARTHENOGENESIS: Production of offspring by females without fertilization by a male All offspring are female Occurs naturally in some worms, insects & reptiles unfertilized egg  male drone

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

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

5 SEXUAL REPRODUCTION Advantages Disadvantages Each offspring is unique More genetic variation within a population Population able to adapt to changes in the environment (recall natural selection) Increased diversity improves chance that some offspring will survive to reproduce Time & energy to find a mate Fewer offspring More time to develop offspring Tends to require more parental care

SIMPLEST FORM OF SEXUAL REPRODUCTION SIMPLE ORGANISMS 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 bacteria Fungi: molds

DIFFERENT SEXES SEXUAL REPRODUCTION MALE FEMALE SPERMATOZOA OVA (EGG) GAMETES are identified as distinctly MALE or FEMALE Separate sex chromosome Y (MALE) or X (FEMALE) Gametes are produced in separate organisms Most advanced form of sexual reproduction MALE FEMALE SPERMATOZOA OVA (EGG)

EXTERNAL FERTILIZATION 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 occurs in aquatic invertebrates, fish, and amphibians.

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

HERMAPHRODITES SEXUAL REPRODUCTION HERMAPHRODITIC organisms Male/female gametes produced within same organism flower pine earthworms

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.