Invertebrates 2

Question 1

Name and describe the 3 stages of embryonic development?

Answer 1

1. Fertilization: Process of combining a haploid sperm cell with a haploid egg cell to form a diploid zygote.
2. Zygote: diploid cell resulting from two haploid gametes (1st cell of next generation)
3. Embryo: young animal still contained within a protective structure(egg shell, uterus)

Question 2

First major process in embryonic development?

Answer 2

After fertilization cleavage occurs.
Cleavage: Multiple round of very rapid mitotic(mitosis) cell division that does not change the volume/size of the organism but instead the process takes one cell and forms many cells from the one.
Produces the blastula

Question 3

Second major process in embryonic development?

Answer 3

Gastrulation: Process in which invagination and in-folding causes the embryo to go from having one-layer of embryonic tissues to having multiple layers.
Produces the gastrula

Question 4

Third Major Process of embryonic development?

Answer 4

Cellular Differentiation: A process where an immature unspecialized cell becomes specialized and reaches it mature form/function.

Question 5

What animals don’t under Goth third major embryonic developmental stage?

Answer 5

Sponges

Question 6

Major feature of the gastrula?

Answer 6

The blastopore is the first opening in the embryo and it will later become either the anus or mouth of the organism

Question 7

What is the outer layer of the gastrula?What does it become?

Answer 7

Ectoderm : becomes the epidermis and nervous system

Question 8

What is the inner layer of the gastrula? What does it becomes?

Answer 8

Endoderm: forms the digestive and respiratory organs

Question 9

What is a diploblast?

Answer 9

An organism with 2 primary germ layers in the blastula: endoderm and ectoderm

Question 10

What is a triploblast? What does the third layer form and in what animals?

Answer 10

An organism with 3 primary germ layers in the blastula: endoderm, ectoderm and mesoderm. Animals with bilateral symmetry are triploblastic. The mesoderm in these animals form most of the internal organs (muscles, skeletal system, gonads)

Question 11

Asymmetrical body symmetry? What animal?

Answer 11

No axis divides the body into equal halves. Only sponges are asymmetrical

Question 12

Radial Symmetry

Answer 12

The organism can be divided into equal parts from many angles (ex. jelly fish)

Question 13

Changing body symmetry

Answer 13

Some organisms body symmetry changes throughout their life. Example: As a larvae a starfish is bilaterally symmetrical, however as an adult a starfish is radially symmetrical

Question 14

Bilateral symmetry

Answer 14

There is only one single axis that divides the body into two equal halves (midsaggital plane: goes between the eyes of the organism)

Question 15

Sponges

Answer 15

-Earliest animals recorded
-Motile as larvae, sessile as adults
-Specialized cells but no organs or true tissues(diploblastic)
-To excrete and respire they use diffusion
-endoskeleton
-Can be radially symmetrical or asymmetrical

Question 16

Sponges: water currents

Answer 16

Sponges are covered in incurrent pores that bring oxygen, water and nutrients into the sponge. They also have an out-current pore(osculum) that gets rid of waste, water and carbon dioxide. To get things in through the pores the flagella of the choanocytes move to create a current that allows water, nutrients and oxygen to enter the pores. The nutrients will then bind to the choanocytes which will digest them and transport them to other cells. Cells will bring CO2 and waste to the choanocytes which release the molecules into the central cavity of the sponge. The molecules will then exit the sponge via the osculum.

Question 17

What is the middle, inner and outer layer of the sponge made up of?

Answer 17

Middle: A jelly matrix that contains ameboid cells.
Outer: Flat epidermal cells
Inner: Choanocytes and their flagella

Question 18

What makes sponges spongy?

Answer 18

In their jelly matrix sponges contain high levels of spongin which causes sponges to have absorbent and soft textures.

Question 19

What causes sponges to be hard and not soft?

Answer 19

High levels of SiO2

Question 20

Do sponges reproduce sexually or asexually?

Answer 20

BOTH

Question 21

Name and explain the two ways sponges can reproduce asexually?

Answer 21

1. Fragmentation: A portion of the sponge breaks off and then regenerates into a completely new organism
2. Internal Budding: Internal buds called gemmules can survive harsh conditions and evolve into an adult when conditions are favourable (grows on the side of an adult sponge then breaks off)

Question 22

What is a gemmule?

Answer 22

Several types of cells enclosed in a protective covering

Question 23

Define Hermaphroditic. Can sponges self fertilize?

Answer 23

Most sponges can produce both eggs and sperms. Sponges cannot self fertilize as they can only make one type of gamete at a time

Question 24

How do sponges reproduce?

Answer 24

“Male” sponge releases sperm into the aquatic environment through the osculum, the sperm will then go into the female sponge in the same way food particles enter the sponge(choanocytes trap the sperm and the cells enter the interior of the organism via pores, the sperm are then delivered to the eggs which are the amoebocytes and fertilizes the egg. The zygote is then released back into the water)
- the sponge larvae then develops into an adult and finds suitable substrate to bind to