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/Disadvan
tages
 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
Advantages/Disadvan
tages
 May have evolved from
mechanisms used by early
life to repair DNA
 Organism must use energy
to produce gametes and
find mate
 Only diploid cells can do
DNA repair
 Quickly makes different
combinations of genes –
creates genetic diversity
which is the raw material of
evolution
 Many enzymes that are
involved in DNA repair are
also involved in meiosis
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