Lesson 1
Understanding Sexual Reproduction in Plants
Next Generation Science/Common Core Standards Addressed!
HS‐LS1‐Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.]
WHST.9‐12.7 Conduct short as well as more sustained research projects to answer a question (including a self generated question) or solve a problem; narrow or broaden the inquiry when appropriate; synthesize multiple sources on the subject, demonstrating understanding of the subject under investigation. (HS‐LS1‐3)
HSSIC.A.1 Understand statistics as a process for making inferences about population parameters based on a random sample from that population. (HS‐LS2‐6)
Bell Work!1. Discuss the importance of plant propagation
2. Explain the difference between sexual and asexual reproduction
3. Identify the major parts of a seed
4. List the function of each major part of a seed
Terms!Cotyledon
Cross pollination
Diploid
Embryo
Endosperm
Epicotyl (plumule)
Fertilization
Gametes
Genes
HaploidHybridsHypocotylPollinationRadicleSeedSeed coatSelf pollinationSexual reproductionZygote
Interest ApproachLook at the sample of plants that I have brought in for you. What are the two categories of plants that are displayed?How important do you think flowers are to a plant?How are plants more successful at reproduction than animals?
What Would Happen if Plants Did Not Have the Ability to Reproduce?Plants are essential for life as we know it on earth
They are the ecological producers of our planetThey produce food and shelter for other organisms, produce oxygen to support animal respiration, and enrich our environment
Throughout history people have relied on seeds and plant parts to grow new plants for food and fiber. Livestock production would be impossible without plants!
In more recent times, knowledge of plant reproduction has resulted in the development of plant hybrids that have enabled large scale agricultural production of food and fiber plants
How Is Sexual Reproduction Different From Asexual
Reproduction?Sexual reproduction occurs when the male sperm carried in the pollen unites with the female egg within a flower
Most plants reproduce their own kind in nature by seeds that are the result of sexual reproduction
The male sex cell (sperm) and the female sex cell (egg) are known as gametes
The union of gametes produces the seed that contains the embryo plant and stores food
Both the male sperm and the female egg contribute genetic information to the new embryo plant
This results in new combinations of genes producing new traits that add vigor to the offspring
The offspring resulting from this new combination of genes is known as a hybrid
People have greatly improved agricultural crops through hundreds of years of hybridization
The genes, made from DNA, are located in chromosomes
Normal cells contain a pair of chromosomes and are said to be diploid
Reproductive cells, the egg and sperm, contain a single chromosome and are said to be haploid
Fertilization unites the single chromosome in the sperm nucleus with the single chromosome in the egg nucleus
This enables the fertilized egg or zygote to have a complete pair of chromosomes (diploid)
Plant fertilization is unique because the sperm contains two nuclei
Causes the plant to become double fertilizedOne sperm nucleus unites with the egg nuclei to produce a zygote
The second sperm nucleus unites with the nuclei of the embryo sac that develops into the endosperm
Fertilization Process
PollenStigma
Ovary
Egg
Two sperm nuclei
Pollen tube
Second nucleus
Egg nucleus
One sperm fertilizes egg
One sperm fertilizes second nucleus to form endosperm
Pollination is the transfer of the male sperm carried in the pollen to the female part of the flower, the stigma
Plants rely on insects, wind and water to transfer the pollen to the stigmaIn addition, plants depend on animals to help with this process
Birds, insects, bats and other animals are attracted to brightly colored, scented flowersThese animals transfer pollen from the anthers of the flowers they visit to the stigmas of other flowers
PollinationPollen grains (contain sperm)
Stigma
Ovule
OvaryEgg cellA bat is covered with pollen from
this flower. It will transfer this pollen to another flower when it searches for more nectar.
Pollination
Pollination
Pollination
Types of PollinationA. When the pollen of a plant pollinates a flower on the same plant, it is called self-pollination
Many plants have this ability, others do not
B. When the pollen of a plant pollinates the flower on another plant of the same species, it is said to be cross-pollination
What Are the Major Parts of a Seed & Where Are They Located?
A seed is a living entity that serves as a bridge between generations of a plant
It is formed in the pistil of the flower and develops from the ovule following fertilization
As the fertilized egg (zygote) grows and develops, it becomes the embryo of the seed
Parts of the EmbryoThe embryo contains the root, stem and leaf of a complete plant
In addition to this, it also contains stored food to support development and growth of the embryo
The seeds of dicot plants have food stored cotyledons. In monocot seeds, most food is found in the endosperm
The embryo’s root is called the radicle, the stem the hypocotyl and the leaf the epicotyl
Surrounding the embryo & endosperm is a protective seed coat
Embryo Parts
Seed coat
Epicotyl
Cotyledons
Hypocotyl
Seed coatEndosperm
Epicotyl
Hypocotyl
RadicleCotyledon
What Is the Function of Each Major Part of a Seed?
Each part of the seed has a specific function to help ensure that a healthy new plant will emerge from the seedThe seed is a living entity which contains the embryo plant & everything necessary for its growth & development
Dicot plants (soybean, pea, oak) have two cotyledons while monocots (corn, coconut, lilies) have only one cotyledon in its seed
Seed Parts & FunctionsRadicle Lower part of the hypocotyl; forms the
first root; first to emerge from the seed
Hypocotyl Develops into the true stem
Epicotyl Above the hypocotyl; develops into a pair of small leaves
Tip is sometimes called the plumule – it is the terminal bud of the first shoot to emerge form the seed
Endosperm Found in monocots in an area of high concentration of food; food source for the embryo
Cotyledon Stores food absorbed from the endosperm when the seed is formed; provides energy until the plant produces its own food
Seed coat Surrounds the seed and protects it from injury and dehydration
SummaryWhy are plants essential on earth?How is sexual reproduction different from asexual reproduction?What is another name for the sex cells of a plant?How is a haploid gene different from a diploid gene?Explain the process of pollination. What are the two types?
Summary ContinuedHow does fertilization in a plant occur?
What part of the seed is the primary root?
What is the function of a cotyledon?
What part of the plant develops into the true stem?
How is a monocot different from a dicot?
What protects the seed before it germinates?
The End!