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