Biology Unit Three D – Asexual Reproduction and Cell Functions Mrs. Pearson’s First Semester Biology *For those watching by recording, watch for questions on the slides throughout the presentation. Email me the answers to the questions within two days of the lesson being presented in order to receive credit for watching the recording.

Lesson Objectives Systems are comprised of smaller interacting parts working together to form a whole Compare and contrast the two rounds of meiosis.

Tissues are groups of cells that perform a similar function. Multicellular organisms depend on interactions among different cell types. vascular tissue leaf stem lateral roots primary root SYSTEMS root system shoot system Tissues are groups of cells that perform a similar function. Organs are groups of tissues that perform a specific or related function. Organ systems are groups of organs that carry out similar functions. CELL TISSUE ORGAN

Always remember… How will you remember the organization levels? Cell – Tissue – Organ – Organ System - Organism

Specialized cells perform specific functions. Cells develop into their mature forms through the process of cell differentiation. Cells differ because different combinations of genes are expressed. A cell’s location in an embryo helps determine how it will differentiate. **Those watching by recording, include in your email the name of the process that causes cells to develop into their mature forms. Outer: skin cells Middle: bone cells Inner: intestines

What if… What if you figured out how to get a cell in a lab to differentiate into a specific kind of cell and then could get it to replicate? What could you do with that ability? Who could that help?

Stem cells are unique body cells. Stem cells have the ability to divide and renew themselves remain undifferentiated in form develop into a variety of specialized cell types **Those watching by recording, include in your email two of the abilities stem cells have.

Controversial Science Why is stem cell research controversial? What could happen to remove the controversy?

Stem cells are classified into three types. totipotent, or growing into any other cell type pluripotent, or growing into any cell type but a totipotent cell multipotent, or growing into cells of a closely related cell family

Stem cells come from adults and embryos. Adult stem cells can be hard to isolate and grow. The use of adult stem cells may prevent transplant rejection. The use of embryonic stem cells raises ethical issues Embryonic stem cells are pluripotent and can be grown indefinitely in culture. First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.

Stem cells are used to treat leukemia and lymphoma. The use of stem cells offers many currently realized and potential benefits. Stem cells are used to treat leukemia and lymphoma. Stem cells may cure disease or replace damaged organs. Stem cells may revolutionize the drug development process. Stem cell and bone marrow donor registry: http://www.marrow.org/index.html?src=tabhome **Those watching by recording, include in your email what stem cells are used to treat.

You have body cells and gametes. Body cells are also called somatic cells. Germ cells develop into gametes. Germ cells are located in the ovaries and testes. Gametes are sex cells: egg and sperm. Gametes have DNA that can be passed to offspring. body cells sex cells (sperm) sex cells (egg)

Your cells have autosomes and sex chromosomes. Your body cells have 23 pairs of chromosomes. Homologous pairs of chromosomes have the same structure. For each homologous pair, one chromosome comes from each parent. Chromosome pairs 1-22 are autosomes. Sex chromosomes, X and Y, determine gender in mammals.

Body cells are diploid; gametes are haploid. Fertilization between egg and sperm occurs in sexual reproduction. Diploid (2n) cells have two copies of every chromosome. Body cells are diploid. Half the chromosomes come from each parent.

Haploid (n) cells have one copy of every chromosome. Gametes are haploid. Gametes have 22 autosomes and 1 sex chromosome.

Chromosome number must be maintained in animals. Many plants have more than two copies of each chromosome. Mitosis and meiosis are types of nuclear division that make different types of cells. Mitosis makes more diploid cells.

Meiosis makes haploid cells from diploid cells. Meiosis occurs in sex cells. Meiosis produces gametes.

Cells go through two rounds of division in meiosis. Meiosis reduces chromosome number and creates genetic diversity.

Pairs of homologous chromosomes separate in meiosis I. Meiosis I and meiosis II each have four phases, similar to those in mitosis. Pairs of homologous chromosomes separate in meiosis I. Homologous chromosomes are similar but not identical. Sister chromatids divide in meiosis II. Sister chromatids are copies of the same chromosome. homologous chromosomes sister chromatids sister chromatids

Meiosis I occurs after DNA has been replicated. Meiosis I divides homologous chromosomes in four phases.

Meiosis II divides sister chromatids in four phases. DNA is not replicated between meiosis I and meiosis II.

Meiosis differs from mitosis in significant ways. Meiosis has two cell divisions while mitosis has one. In mitosis, homologous chromosomes never pair up. Meiosis results in haploid cells; mitosis results in diploid cells.

Haploid cells develop into mature gametes. Gametogenesis is the production of gametes. Gametogenesis differs between females and males. Sperm become streamlined and motile. Sperm primarily contribute DNA to an embryo. Eggs contribute DNA, cytoplasm, and organelles to an embryo. During meiosis, the egg gets most of the contents; the other cells form polar bodies.

Review Binary fission is similar in function to mitosis Asexual and sexual reproduction each have advantages and disadvantages Multicellular organisms depend on interactions among different cell types Specialized cells perform specific functions Cells develop into their mature forms through the process of cell differentiation Stem cells are cells that have not differentiated yet

Questions?