week 23

Question 1

what was LECA

Answer 1

a single-cell organism which predominantly reproduced by mitosis, not meiosis.

Question 2

what does fission mean

Answer 2

division into two equally-sized offspring

Question 3

what does budding mean

Answer 3

unequal divison; smaller offspring

Question 4

what does fragmentation mean

Answer 4

the parent breaks into many small new individuals

Question 5

what is phylogeny

Answer 5

study of evolutionary history and relationships between groups of organisms

Question 6

what are the two sexes in higher plants

Answer 6

pollen and ovules

Question 7

what is the r number and what does it mean

Answer 7

the reproduction number. R of 1= population stays the same per generation. R of 2= population doubles per generation.

Question 8

name some costs of sexual reporduction

Answer 8

two individuals needed, costly for R number.
need to locate a mate.
need two different gametes

Question 9

what are cavendish plants

Answer 9

they are sterile (no seeds)- asexual reproduction. all are clones and are susceptible to Panama disease

Question 10

what are hermaphrodites

Answer 10

they generate both male and female gametes

Question 11

what is klinefelter syndrome

Answer 11

Phenotypic males with XXY resulting in infertility

Question 12

what is turner syndrome

Answer 12

phenotypic females with X0 (one X) resulting in infertility

Question 13

what is the SRY gene

Answer 13

sex-determining region of Y on males (testis determining factor)

Question 14

what do Leydig cells do

Answer 14

produce the steroid hormone testosterone

Question 15

what are the roles of WNT4 and SOX9 proteins in sexual determination

Answer 15

WNT4- active in female embryo
SOX9- active in male embryo

Question 16

what generates ovaries and testes in the mammalian embryo

Answer 16

the SRY sex determination pathway

Question 17

when is sex determined in humans

Answer 17

6 weeks after fertilisation, when the SRY gene is first expressed (males) or not expressed (females)

Question 18

when does gonad development start

Answer 18

Indifferent gonad development starts early, but has no sex-specific features until after sex determination

Question 19

what are genital ridges

Answer 19

structures in early embryonic development that contain somatic gonadal precursor cells and gove rise to gonads

Question 20

how to genital ridges differentiate into the indifferent gonad

Answer 20

genital ridges contain somatic gonadal precursor cells. Germline stem cells migrate into the genital ridge. The genital ridge becomes the indifferent gonad

Question 21

what is gametogenesis

Answer 21

process where gametes (sex cells) are formed from germ cells in the gonads (ovaries in females, testes in males)

Question 22

what are Sertoli cells

Answer 22

necessary for sperm production in males, promote spermatogenesis

Question 23

what are spermatogonia

Answer 23

cells in the testes which give rise to mature sperm through a process called spermatogenesis

Question 24

what are sex-specific differences in gametogenesis in humans

Answer 24

Oogenesis produces a single large ovum vs. the male process (spermatogenesis), which produces four tiny sperm. In females, one oocyte is usually selected to mature per 28-day ovarian cycle. In males, continued mitotic divisions of spermatogonia through most of life.

Question 25

what is the capacitation and acrosome reaction

Answer 25

acrosome- the organelle surrounded by plasma membrane on the sperm, containing sperm receptor for egg protein and other enzymes. Capacitation- occurs in female tract as sperm swims. The acrosome membrane fuses with the sperm cell membrane, exposing sperm receptor for egg protein. sperm is now primed, ready to fuse with egg

Question 26

what is a blastocyte

Answer 26

6 day old human embryo

Question 27

what is the trophoblast

Answer 27

Outer layer of cells part of the placenta but not the embryo. secretes enzymes

Question 28

what component of the blastocyst does the embryo almost entirely develop from

Answer 28

The epiblast.

Question 29

how are aquatic embryo development systems simpler than terrestrial

Answer 29

they are just an embryo, no placenta or extra-embryonic structures

Question 30

what is a blastula

Answer 30

a ball of cells (blastomeres) with a fluid-filled cavity called a blastocoel. cells of the early blastula are totipotent, cells progressively loose totipotency as they commit to cell fates.

Question 31

what are amniotes

Answer 31

a large tetrapod (4 limbs) vertebrate animal group (including humans) with an amnion.

Question 32

what is an amnion

Answer 32

a fluid-filled sac surrounding the embryo of amniote organisms. the fluid has the same salt concentration as the ocean

Question 33

what is hCG

Answer 33

a hormone produced by pregnancy, secreted in urine and identified by pregnancy tests. secreted from the trophoblast until later in pregnancy where the placenta stops making hCG.

Question 34

what is the corpus luteum

Answer 34

a temporary endocrine gland forming after ovulation, if fertilisation occurs, the corpus luteum is maintained by the trophoblast and hCG and secretes estradiol and progesterone.

Question 35

when does the corpus luteum degenerate

Answer 35

after ovulation if fertilisation does not occur. if fertilisation occurs the corpus luteum doesnt degenerate until 2nd/ 3rd trimester later in pregnancy.

Question 36

how is the immune system altered during pregnancy

Answer 36

the immune system becomes more tolerant of the foetus foreign antigens, preventing rejection

Question 37

when is the placenta developed and producing estrogen and progesterone

Answer 37

week 5

Question 38

define cell potency

Answer 38

a cells capacity to generate different kinds of specialised cells

Question 39

define the term terminally differentiated

Answer 39

a fixed single cell type

Question 40

what are monoblasts

Answer 40

only one layer blast cells. no true tissues e.g. sponges

Question 41

what are diploblasts

Answer 41

only two layers blast cells. a digestive cavity, one opening which serves as mouth and anus e.g. jellyfish

Question 42

what are triploblasts

Answer 42

three layers of embryonic blast cells- each layer restricted to different future potentials. a mouth, anus and gut in between. e.g. humans

Question 43

define gastrulation

Answer 43

a movement and reorganisation of cells that is linked to creation of three fundamental layers of blast (or stem) cells in the early embryo.

Question 44

what are the three primary germ layers which form during early embryonic development

Answer 44

ectoderm, mesoderm and endoderm. These have very different restricted pluripotency

Question 45

what are bilateria

Answer 45

Organisms with bilateral symmetry and are all triploblastic. they have anterior/ posterior, dorsal/ventral

Question 46

what are homeotic genes

Answer 46

genes which determine the identity of body segments or structures during embryonic development, they encode transcription factors

Question 47

what is the hox gene cluster

Answer 47

a cluster of related homeotic genes. expression of HOX proteins is a global positioning system, giving regional identity in animals.

Question 48

what is synpolydactyly

Answer 48

a genetic condition caused by a mutation in the human homeotic gene. many severe suspects die before birth

Question 49

how does the homeotic gene work to control the identity of body structures

Answer 49

by regulating the expression of other genes to control differentiation.

Question 50

what is the Cambrian explosion

Answer 50

a period of rapid diversification of animal life