Grade 8: Reproduction

Big Idea: Reproduction is necessary for the _______________________ if every species.

continuation

Characteristics of living things (requirements to be considered alive)

1. have/are made of cells

2. sense and respond to change

3. use energy

4. have DNA

5. grow and develop

6. reproduce

Cell Theory

1. All organisms are made of one or more cells.

2. The cell is the basic unit of all living things-begin as a single cell.

3. All cells come from existing cells.

Smallest unit that can perform life processes

Cells

Asexual Reproduction

-single parent produces offspring that are genetically identical to the parent

- simple organisms

Mitosis

-cells reproduce exact copies of themselves;

-daughter cells are identical to each other & identical to parent cell

-produces 2 daughter cells

-divides once

Sexual Reproduction

-an egg from one parent combines with a sperm from the other parent (two parents)

-produce offspring with a mix of genetic material

- most animals & many simple &

complex organisms

Meiosis

-process which produces sex cells (called gametes), which have half the number of chromosomes

-cell divides twice and creates 4 daughter cells

- these 2 halves combine during reproduction

- daughter cells are genetically different from the parent cell and each other

Methods of asexual reproduction:

fragmentation & regeneration

budding

runners

tubers

binary fission

mitosis

Budding (plantlets)

one part of an organism pinches off a parent organism

examples: yeast, hydra, ferns, succulents)

Runners

sending out shoots along the ground making new plants asexually (strawberry)

Fragmentation and Regeneration

parts are broken off (injury) and develop into a new organization

examples: sea star

binary fission

one celled organism divides into two identical organisms

example: bacteria only

After fertilization, which part of plant becomes a fruit?

ovary

After fertilization, which part of plant becomes a seed?

ovule

What is contained in eukaryotic cell's nucleus ?

DNA, the cell's genetic material

Gametes

(sex cells) special cells that contain half of the genetic information from a parent (23 chromosomes)

Male sex cell

sperm

Female sex cell

egg

After an egg has been fertilized, the new organism is called?

zygote

After the zygote divides and becomes a small mass of cells that develop into living organism it is called ?

embryo

Gestation

growth process of an embryo inside a mother - common in mammals

External fertilization (outside the body)

- must have a moist environment to allow the sperm to meet the egg

- often involves many parents and many offspring to ensure survival from predators

-mostly amphibians and fish

Internal fertilization (inside the body)

-occurs within the body of the female

-protection means that less eggs (offspring) are needed to ensure survival

-lay fertilized eggs (birds & reptiles)

-zygote develops inside mother & live birth (mammals)

Fertilization

genetic material of the gametes is combined into a new genetic individual

Sexual Reproduction -pros and cons

Pros- genetic diversity, creates complex organisms, allows for group immunity

Cons- slow, energy inefficient, inconsistent, and requires a long time for organisms to grow and develop

Asexual Reproduction- pros and cons

Pros- faster, more energy efficient, more consistent, and allows for more organisms to mature faster

Cons- offspring are genetically identical and little variety is possible

plants structures used in asexual reproduction

tubers, plantlets, runners, rhizomes

Male reproductive part of a flower

stamen

Female reproductive part of a flower

pistil

"biological imperative" idea

Organisms are driven to reproduce, otherwise the species will go extinct.

What is needed for a flower to become a fruit?

pollination and fertilization

Seeds are

baby plants and have the complete genetic material.

pollen

A fine dust that contains the sperm of seed-producing plants

simple organisms

-able to use forms of asexual reproduction to regrow and become new separate individuals

- first creatures on the planet must have used these strategies to reproduce