Sexual Reproduction In Animals and Plants Differences between sexual and asexual reproduction Advantages and disadvantages of each type of reproduction How plants reproduce
Jan 13, 2016
Sexual Reproduction In Animals and Plants
Differences between sexual and asexual reproduction
Advantages and disadvantages of each type of reproduction
How plants reproduce
Reproduction can be asexual or sexual
Asexual reproduction – single parent passes copies of all its genes to offspring Offspring is a clone of its parent Prokaryotes and some eukaryotes can reproduce asexually
Sexual reproduction – two parents form reproductive cells that have half the number of chromosomes of parents Offspring have traits of each parent but is genetically
different from each Eukaryotes can reproduce asexually
Asexual Reproduction
Types
Fission
Fragmentation
Budding
Advantages/Disadvantages
Asexual reproduction simplest and most primitive form of reproduction
Produce many offspring in short period of time
Little genetic variation – problem in changing environment
Sexual Reproduction
Evolution
May have evolved from mechanisms used by early life to repair DNA
Only diploid cells can do DNA repair
Many enzymes that are involved in DNA repair are also involved in meiosis
Advantages/Disadvantages
Organism must use energy to produce gametes and find mate
Quickly makes different combinations of genes – creates genetic diversity which is the raw material of evolution
Sexual Life Cycles of Eukaryotes
Animals have a diploid life cycle – life cycle is dominated by diploid stage – which produces haploid gametes – which fuse to form diploid zygote
Plants have a life cycle that alternates between diploid and haploid Diploid phase in plants called sporophytes Sporophytes produce haploid spores by meiosis Spores develop into haploid multicellular individuals called
gametophytes without fusing with another cell Gametophyte produces haploid gametes by mitosis. Gametes fuse and give rise to the diploid phase
Plant Life Cycle
Complex plants have sporophytes and gametophytes that appear very different
In mosses, the haploid gametophyte is dominant
In flowering plants, the diploid sporophyte generation is dominant
Reproduction in Seed Plants
Seed plant gametophytes are made up of only a few cells
Male gametophytes produce pollen
Ovule
Female gametophytes develop within an ovule – which is part of the sporophyte. After fertilization by pollen – the ovule and its contents develop into a seed
Seed plants can reproduce sexually without water –wind, insects and birds carry pollen to the female parts of the plant - pollination
Seeds
Seeds contain the embryos of plants
An embryo is a new sporophyte
Outer layers of ovule harden to form protective seed coat
Leaf-like structures called cotyledons are part of plant embryo – they provide nutrients to embryo
Flowers
Gametophytes develop within flowers
Outermost whorl = sepals
Second whorl = petals (these are brightly colored to attract birds and insects)
Stamen – produces pollen; consists of anther and filament
Pistil – produces ovules; consists of ovary, style and stigma (sticky part where pollen sticks)
Fruit
Structure of the plant that contains the seed
Develops from one or more of the flower’s ovaries
Apples, tomatoes, avocados, cucumbers, pumpkins, okra – anything that contains seed(s) is a fruit
Vegetables
Other part of plant that we eat – leaf, root, stem…
Any part of the plant that we eat that does not contain the seed
Celery, carrots, potatoes, spinach, etc….
Parts of plant not directly involved in reproduction