Announcements 1.Homework #1 - finish your quizzes! 2.Thinking about a quiz in lab … 3.Test #1 April 20 th – bring a 50 question scantron

Biology Main points/Questions 1.What do you remember about fungal life cycles? 2.What is the difference between growth and development? 3.How do plants keep growing for their entire lives? 4.How do animal cells differentiate?

Quick quiz but first… How well do you understand the following (scale of 1-5, 1= fully, 3=some, 5 = not at all) –Fungal life cycles –Reproduction in Ferns –Early animal develop. (cleavage  gastrula)

Fungal life cycles main ideas: 1.Meiosis produces 2.These structures (from 1) divide (mitosis) to become a “thread-like” that grow into a mat called a. Any cell can fuse with a cell of another mating type (no specialized gametes!) 3.Cytoplasm joins when cells fuse but initially not the nucleus creating a cell!

4. These structures on the back of a fern frond are called. 5. They produce that grow into the generation.

6. During development animals grow into a hollow ball of cells called a.

Fungal life cycles main ideas: 1.Meiosis produces Spores 2.These structures (from 1) divide (mitosis) to become a “thread-like” hyphae that grow into a mat called a mycellium. Any cell can fuse with a cell of another mating type (no specialized gametes!) 3.Cytoplasm joins when cells fuse but initially not the nucleus creating a Dikaryotic cell!

4. These structures on the back of a fern frond are called Sori. 5. They produce Spores that grow into the Gametophyte generation.

6. During development animals grow into a hollow ball of cells called a Blastula.

Using the quiz results Did you remember the information from last time? From the time before? Did you confuse familiarity with more in depth knowledge? How much will you remember on Tuesday for the lab quiz? On April 19 th for the 1 st exam?

Growth & Development Both plants and animals start off their diploid phase as a single fertilized egg During development genetically identical cells differentiate as genes are turned on and off. This causes cells to develop into specialized tissues, a group of cells of similar appearance and function. Developmental patterns determine which type of tissues develop in which region.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Plant and Animal development patterns

To understand we need to look a little more at plant reproduction

Plant growth and development Remember the life cycle of plants?

Look at these moss plants. Where are the sporophytes? the gametophytes?

Where are the two generations?

Plant growth and development In flowering plants the gametophyte generation is very small and comes in male and female versions The female, egg producing gametophyte, is completely retained on the sporophyte. The male gametophyte is Pollen! Both are produced on flowers

Fig Anther Ovary

Fig Male Gametophyte is inside here! It is a pollen grain Female Gametophyte is inside here! Called an embryo sac

Anthers with pollen Pollen grains

In flowering plants the entire male gametophyte plant (pollen) is transferred to the location of the female gametophyte (ovary) We call this pollination and it is different from fertilization. After the pollen gets transferred it still must grow to the female gametophyte and fertilize the egg. Pollination vs fertilization

Fig a Ovary Pollen must get transferred here (pollination) But the egg is all the way down here

Pollen tube 2 sperm Egg Pollen grain Pollen grows down to the egg. Fertilization occurs down here

Ovary Ovule Egg Pollen grain The egg develops inside a structure called an ovule found in the ovary

Ovule Egg 2 sperm Fertilization is tricky… both sperm fertilize things… one fertilizes egg, one fertilizes 2 nuclei

Endosperm nucleus (3n) (2 polar nuclei plus sperm) Zygote (2n) (egg plus sperm) So we get diploid zygote and triploid endosperm (it is used for nutrition later)

Development in plants We have seen in flowering plants: –Fertilization happens inside the ovule Now lets look at how the embryo develops –In flowering plants we pack the embryo in a seed. –Seeds contain the embryo & food supplies –Seeds of flowering plants are found surrounded by fruit

Development in plants Where do these structures come from? They develop from structures already present in the flower! –Ovary  fruit –Ovule  seed coat –Zygote  embryo –Endosperm  nutritive tissue inside seed

Relationship between a pea flower and a fruit (pea pod)

In the peanut Where is tissue from the parent plant? Can you see ovule? Ovary? What part is the embryo? –Can you see specialized regions of the embryo? –Look for a root tip and leaves Endosperm in the peanut is gone – consumed to fuel development of the peanut.

Development in plants From:

Peanut flower but…

Peanuts harvested from underground…

Development in plants From:

Development in plants As the zygote undergoes mitosis it specializes different tissues Unlike the animals plants maintain regions of undifferentiated tissues (called meristems) –This tissue is capable of dividing and forming any other plant tissue –Plants have meristem at the tips of all growing shoots and roots –This pattern is set up inside the seed.

Development into a seed When the zygote divides the cells recognize their position in the ovule. They use this information to alter gene expression. Cells near the base start to divided differently becoming the embryonic root

Development into a seed Cells “higher” up will start to become the embryonic shoot & leaves But remember that some cells remain undifferentiated (they haven’t committed to develop a certain way)

Meristem tissue ready for when the seed germinates

Fig b Seed development can be modified as in the peanut…

Fig a

Development in plants While the seed is developing the rest of the flower also changes Ovary tissue develops into the fruit that surrounds the seed(s)

Fig a

Fig b So what do animals do?

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 21.2

(a) Fertilized egg All animals start out as a fertilized egg that undergoes mitosis. In deuterostomes (?) cells divide at right angles while in protostomes (?) they divide in a spiral pattern

Animal Development We will focus on two basic strategies for development seen in two major groups –Protostomes include arthropods and mollusks –Deuterostomes include all the chordates These groups have several differences in their development we focus on 3 –Cleavage pattern –Timing of cell specialization –Fate of blastopore

Eight-cell stage Spiral and determinateRadial and indeterminate Protostome development (examples: molluscs, arthropods ) Deuterostome development (example: chordates)

(b) Four-cell stage In mammals these cells can be separated and each will produce a separate identical embryo – deuterostome development Other organisms (protostomes - like arthropods and mollusks) specialize each cell as it is made. Pull one off and the embryo will not develop.

(c) Early blastula In many animals in both groups the cells divide and produce a hollow ball of cells called a blastula.

(d) Later blastula Specific cells on the outside of this ball then “crawl” up inside the hollow space in a process called gastrulation

During gastrulation cells further specialize into three embryonic tissues –Endoderm – the innermost cells –Mesoderm – cells in the middle –Ectoderm – cells that remain on the outside This process also creates an opening into the ball called a blastopore Video: Sea Urchin Embryonic Development Video: Sea Urchin Embryonic Development

Zygote Cleavage Eight-cell stage

Zygote Cleavage Eight-cell stage Cleavage Blastula Cross section of blastula Blastocoel

Zygote Cleavage Eight-cell stage Cleavage Blastula Cross section of blastula Blastocoel Gastrulation Blastopore Gastrula Archenteron Ectoderm Endoderm Blastocoel

Protostomes and Deuterostomes We have seen: –Cleavage pattern differences, spiral vs. radial –Timing of cell specialization differences The last difference we look at is the fate of the blastopore. –As the embryo develops the open space inside the gastrula will be the digestive tract – the blastopore will be one of the openings – either the mouth or the anus.

Anus Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Anus Mouth Digestive tube (c) Fate of the blastopore Key Ectoderm Mesoderm Endoderm Mouth develops from blastopore.Anus develops from blastopore. As embryos continue to develop tissues continue to specialize Each of these 3 embryonic tissues will give rise to numerous tissues/organs in the adult