1.4 - Animal bodies

Question 1

what are the common characteristics of animals? (3)

Answer 1

1. heterotrophic (cannot produce own food), multicellular eukaryotes
2. multiple specialised cell types that form organs
3. usually mobile

Question 2

Describe metazoans (2)

Answer 2

1. Animals, form single clade within eukaryotes
2. occupy distinct geological niche as multicellular heterotrophic organisms

Question 3

Describe ediacaran ecology (4)

Answer 3

1. multicellular animals appear after 3b years of life on earth
2. animals had limited mobility
3. no fierce predators
4. short food chains

Question 4

describe what happened at the cambrian explosion

Question 5

name the 3 main phyla (3)

Answer 5

1. Nematoda
2. Arthropoda
3. Chordata

Question 6

how are the animal phyla recognised? (2)

Answer 6

1. early development (gastrulation)
2. bodily structure

Question 7

Describe gastrulation

Answer 7

vital process in early embryonic development when a developing embryo transforms from single layer of cells into multilayered structure, called a gastrula, that’s made up of three germ layers

Question 8

what are the 3 germ layers of the gastrula

Answer 8

1. Ectoderm - outer layer
   2.Mesoderm - middle layer
   3.Endoderm - inner layer

Question 9

How does development diverge between protostomes and deuterostomes in early development?

Answer 9

1. protostomes - blastopore becomes mouth
2. deuterostomes - blastopore becomes anus

Question 10

what is the name for a body formed of repeating segments?

Answer 10

metamerism

Question 11

what is segmental specialisation?

Answer 11

segments vary but always some head specialisation for feeding and sensory organs

Question 12

describe tagmosis

Answer 12

fusion of segments, each body section = tagma

Question 13

describe a model species

Answer 13

species commonly used for research

Question 14

name the 4 dominant model species (4)

Answer 14

1. Drosophila
2. Caenorhabditis
3. Zebrafish
4. Mouse

Question 15

why is the Caenorhabditis Elegans a model species? (2)

Answer 15

1. adults have fixed number of cells (959 including 302 neurons + germ cells)
2. Lineage of each cell precisely known - allows study of genetic mechanisms of development

Question 16

How do vertebrates and arthropods bodies (repeating segments) develop in embryogenesis? (5)

Answer 16

1. Maternal effect - genes determine anterior-posterior axis + induce gap genes
2. Gap genes - define several broad areas + regulate pair rule genes
3. Pair rule genes - refine segment location + regulate segment polarity genes
4. Segment polarity genes - determine boundaries and anterior-posterior orientation of each segment
5. Hox genes - together gap, pair rule and segment polarity genes control expression of hox genes (define identity of each segment)

Question 17

What is the role of Maternal effect? (stage 1 - embryogenesis)

Answer 17

genes determine anterior-posterior axis + induce gap genes

Question 18

What is the role of Gap genes? (stage 2 - embryogenesis)

Answer 18

define several broad areas + regulate pair rule gene

Question 19

What is the role of Pair rule genes? (stage 3 - embryogenesis)

Answer 19

refine segment locations + regulate segment polarity genes

Question 20

What is the role of Segment polarity genes? (stage 4 - embryogenesis)

Answer 20

determine boundaries and anterior-posterior orientation of each segment

Question 21

What is the role of Hox genes in embryogenesis?

Answer 21

Expression controlled by gap, pair rule and segment polarity genes - define identity of each segment

Question 22

What is collinearity?

Answer 22

When the Hox genes along the anteroposterior axis of the embryo match the array of genes along the chromosome

Question 23

Mouse Hox genes