Download Lesson 8: Life Cycles

Lesson 8: Life Cycles
California Education Standards:
Kindergarten Life Sciences
2. Different types of plants and animals inhabit the earth. As a basis for understanding this
concept:
a. Students know how to observe and describe similarities and differences in the
appearance and behavior of plants and animals (e.g., seed-bearing plants, birds, fish,
insects).
c. Students know how to identify major structures of common plants and animals (e.g.,
stems, leaves, roots, arms, wings, legs).
Grade 1, Investigation and Experimentation
4. Scientific progress is made by asking meaningful questions and conducting careful
investigations. As a basis for understanding this concept and addressing the content in the other
three strands, students should develop their own questions and perform investigations. Students
will:
a. Draw pictures that portray some features of the thing being described.
b. Record observations and data with pictures, numbers, or written statements.
d. Describe the relative position of objects by using two references (e.g., above and next
to, below and left of).
e. Make new observations when discrepancies exist between two descriptions of the same
object or phenomena.
Grade 2, Life Sciences
2. Plants and animals have predictable life cycles. As a basis for understanding this concept:
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a. Students know that organisms reproduce offspring of their own kind and that the
offspring resemble their parents and one another.
c. Students know many characteristics of an organism are inherited from the parents.
Some characteristics are caused or influenced by the environment.
d. Students know there is variation among individuals of one kind within a population.
e. Students know light, gravity, touch, or environmental stress can affect the germination,
growth, and development of plants.
f. Students know flowers and fruits are associated with reproduction in plants.
Grade 3, Life Sciences
3. Adaptations in physical structure or behavior may improve an organism’s chance for survival.
As a basis for understanding this concept:
a. Students know plants and animals have structures that serve different functions in
growth, survival, and reproduction.
Grade 4, Life sciences
3. Living organisms depend on one another and on their environment for survival. As a basis for
understanding this concept:
c. Students know many plants depend on animals for pollination and seed dispersal, and
animals depend on plants for food and shelter.
Grade 7, Focus on Life Sciences
Genetics
2. A typical cell of any organism contains genetic instructions that specify its traits. Those traits
may be modified by environmental influences. As a basis for understanding this concept:
a. Students know the differences between the life cycles and reproduction methods of
sexual and asexual organisms.
b. Students know sexual reproduction produces offspring that inherit half their genes from
each parent.
c. Students know an inherited trait can be determined by one or more genes.
Vocabulary:
Adult – a living thing that is full-grown and can reproduce
Life Cycle – the changes organisms go through as they develop from eggs or seeds to adults that
reproduce before they die
Offspring – the young of a parent
Reproduction – how plants and animals make new plants and animals like themselves
Genes – the parts of the cell that carry the information that determines the traits, or
characteristics that each individual has
Pollen – the male reproductive part of seeding plants
Stigma – the female reproductive part of seeding plants
Pollinators – insects that spread pollen from flower to flower
Germinate – when a seed sprouts
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Objective:
Students understand how different types of organisms reproduce and pass their genes on to future
generations.
Lesson:
All plants and animals produce offspring of their own species, and go through life cycles that can
be very similar but also different in many ways. For example, all plants and animals that
reproduce sexually start life as an egg. Even humans start as eggs – the difference is that we,
along with other mammals, grow inside our mothers and are born alive and breathing. Most other
animals lay their eggs, and the babies later hatch out of their eggs. Plants start as seeds, which
are very similar to eggs. Both are the reproductive cell created by the female parent, and contain
half of the genes of the offspring. The other half of the offspring’s genetic material comes from
the male’s reproductive cell.
There are thousands of genes in each cell in the human body; in fact, there are genes in the cells
of every living thing. The genes are the parts of the cell that carry the information that
determines the traits, or characteristics, that each individual has. This is why the characteristics
of every organism are inherited from its parents – because all its genes come from the parents.
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Characteristics such as eye color, hair color, and curly or straight hair are all inheritable traits,
and come from your genes. Some traits can be influenced by the environment. For example, your
potential height depends on your genes from your parents, but you may not grow to be tall if you
don’t have proper nutrition in your diet. Many traits are determined by more than one gene, and
this leads to lots of variation within species. For example, if one parent has blue eyes and the
other has brown eyes, their kids could either have blue or brown eyes. This is important because
if there was only one gene for each trait, everyone would be the same!
In plants, sexual reproduction happens in flowers of the plant. The pollen of the flower contains
the male reproductive cells, and when pollen lands on the stigma, it joins with the female
reproductive cells to form a seed. Often, the flowers need help from an insect to spread the
pollen to the stigma, and the insects that do this for them are called pollinators. An example of a
very important pollinator is a bee.
Without pollinators, many plants would not be able to reproduce! Once the seeds are created, a
protective layer grows around the seeds. This layer is the fruit of the plant, the part that we love
to eat. The fruit is also useful because animals like to eat it, and then they spread the seeds
around when they poop, so that the seeds can grow into new plants. The conditions around the
seed such as moisture, temperature, and exposure to sunlight will affect when it germinates, or
starts growing from the seed, and how well it grows.
Although most organisms reproduce sexually, some reproduce asexually. Asexual reproduction
is when an organism makes a copy of itself without combining its genes with those of another
adult of its kind. Some examples of asexual reproducers are sea anemones and bacteria. The
bacteria cell reproduces by splitting into two cells. We humans can help plants reproduce
asexually by taking clippings and replanting them. This is called propagation.
FUN FACT! Did you know that every egg is only one cell? Most cells are so small that we can’t
even see them! The largest cell in the world is an ostrich egg.
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Materials:
Plants from the garden in different stages of the life cycle.
Activities:
What Are We Eating?
Docents lead students in groups of five. Help students find all the different edible plant parts in
the garden, and ask them what part of the plant this is. For example, a tomato is a fruit, carrots
are roots, and the lettuces that we eat are leaves. Ask the students what each of these parts of the
plant are useful for. The fruit protects the seeds, the roots provide water to the plant, and the
leaves are where photosynthesis takes place. Ask the students what nutrition we get from each of
these different parts. For example, we get calcium, iron, and lots of vitamins from leafy greens
such as kale and spinach.
Life Cycles
Procedure:
1. Arrange plants at different stages of the life cycle on a table. Each one of these examples
should be on the table with two or three extra to make it more interesting.
Here are some pictures of the dead, flowering, seedling, and fruiting stages respectively.
Note: You can have a contest with the older grades or just a question and answer period with lots
of back and forth. There were some tricks on the table. Place a couple of cuttings planted in
vermiculite/perlite mixture that they thought were young plants. This will give you a chance to
explain cloning or vegetative reproduction.
2. The rest of the hour is spent by planting cucumber seeds into pots and watering them. This is
the start of an ongoing project throughout several lessons that allows students to visually see the
growth of the plant and its entire life cycle.
Note: Take measurements of the height of the plant each week and take a picture of it during
each session.
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Sources and Links:
http://www.youtube.com/watch?v=chNwmpqSa78 (video)
http://kidshealth.org/kid/talk/qa/what_is_gene.html
http://www.biology4kids.com/files/plants_reproduction.html
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