Life Moves Onto Land

Question 1

Name the three major photosynthetic eukaryotes that descended from cyanobacteria.

Answer 1

Glaucophyta, Viridiplantae and Rhodophyta

Question 2

What features distinguish Glaucophyta?

Answer 2

Chlorophyll A, Phycobillosomes and walled Chloroplasts.

Question 3

What features distinguish Viridiplantae?

Answer 3

Viridiplantae are green algae that evolved into plants, they contain chlorophyll A and B.

Question 4

What features distinguish Rhodophyta?

Answer 4

Red algae containing chlorophyll A and Phycobillosomes.

Question 5

When was the earliest evidence for Eukaryotic sexual reproduction?

Answer 5

1.2Ga (red alga fossils)

Question 6

What is the concept of alternations of generations?

Answer 6

Alternation of generations is a biological process where organisms alternate between two distinct forms: a haploid (n) phase and a diploid (2n) phase. Each phase represents a generation, and the process allows for both sexual and asexual reproduction.

Question 7

What is the Gametophyte phase?

Answer 7

This is the haploid (n) stage of the organism’s life cycle. Haploid spores grow into a gametophyte through mitosis. The gametophyte produces gametes (sperm and eggs) via mitosis. Since the organism is already haploid, mitosis can create more haploid cells. These gametes eventually fuse during fertilization to form a diploid zygote.

Question 8

What is the Sporophyte phase?

Answer 8

This is the diploid (2n) stage, beginning when a zygote is formed. The zygote divides by mitosis to develop into a sporophyte, a multicellular diploid organism. The sporophyte then undergoes meiosis to produce haploid spores. These spores disperse and grow into new gametophytes, restarting the cycle.

Question 9

Chlamydomonas Reinhardtii

Answer 9

-Green alga
-Haploid most of the time
-Sexually reproduces when stressed (survival mechanism)
-2 distinct sexes (gametophytes) which fuse to produce a zygote via meiosis

Question 10

Ulva Lactuca-Sea lettuce

Answer 10

-The gametophyte and sporophyte are co-dominant and have a similar appearance
-produces gametes that combine with other gametes to form a diploid organism (mitosis)
-produces zoospores via meiosis which develop into the gametophyte organism

Question 11

When and why did plants move onto land?

Answer 11

~500Mya following the Cambrian explosion
-increased oxygen levels
-stronger ozone layer
-more space
-more carbon dioxide

Question 12

Challenges of moving onto land.

Answer 12

-issues retaining water
-lack of structural rigidity
-needed water to reproduce
-had to evolve to tolerate non saline water

Question 13

What are Bryophytes?

Answer 13

Bryophytes are a group of non-vascular plants that includes mosses, liverworts, and hornworts. They are among the simplest land plants and are distinguished by their lack of vascular tissues (xylem and phloem), which limits their size and requires them to grow in moist environments.

Question 14

What are Pteridophytes?

Answer 14

Pteridophytes are a group of vascular plants that reproduce via spores rather than seeds. This group includes ferns, horsetails, clubmosses, and whisk ferns. They are some of the earliest vascular plants, with their evolution dating back to around 400 million years ago, making them pioneers in adapting to life on land.

Question 15

Liverworts

Answer 15

-Dominant gametophyte
-Thalloid or leafy structure
-specialised cells
-Rhizoids grow down to absorb water (primitive water transport)
-produces spores

Question 16

Moss

Answer 16

-leaf like structure
-simple water conducting tissues
-ombrotrophic (all water and nutrients from rain)
-sporophytes grow on stems above the gametophyte
-sporophytes have a cuticle layer, stomata and controlled desiccation

Question 17

Hornworts

Answer 17

-Thalloid gametophyte
-horn-like sporophytes that grow upward
-can be blue-green forming a symbiotic relationship with cyanobacteria a nitrogen fixer

Question 18

What are the major clades of athropods?

Answer 18

Hexapoda-6 legs, a head, a thorax and abdomen (insects)
Arachnida-8 legs and chelicerae jaws (spiders)
Myriapoda-elongated bodies with many segments and numerous legs (millipedes)

Question 19

What are Tetrapoda?

Answer 19

vertebrates with 4 legs/appendages (amphibians, reptiles, birds and mammals)

Question 20

Give 2 examples of the lobe finned fish that were part of the biological lineage of animals moving onto land.

Answer 20

Coelacanths-ancient deep marine fish
Lungfishes-live in fresh water, can breath and ‘walk’

Question 21

What provided the earliest evidence for life moving onto land and give an example.

Answer 21

Trace fossils-Diplichnites is an arthropod trace fossil trackway from the Middle Ordovician of the Lake District UK.

Question 22

What is the Rhynie Chert?

Answer 22

An unusual Early Devonian terrestrial deposit preserving plants and animals in
fine detail. (hot spring ecosystem in Scotland)

Question 23

What is Tiktaalik?

Answer 23

Tiktaalik is a key transitional fossil from the Upper Devonian. It had an important mix of characteristics such as an enlarged humerus for walking and a flexible neck for looking around.

Question 24

What is a molecular clock?

Answer 24

A molecular clock is a technique used to estimate the time of divergence between species or lineages based on the mutation rate of biomolecules. It assumes that genetic mutations accumulate at a relatively consistent rate over time.

Question 25

What are the challenges posed by living on land?

Answer 25

-Homeostasis (managing water, oxygen and temp.)
-respiration (spiders use book lungs and insects have a tube system)
-movement
-reproduction

Question 26

What physiological features adapted as life moved onto land?

Answer 26

-Abundant oxygen meant that arthropods became very large
-internal fertilisation
-adapted sensory structures
-bones structure changed to enable walking or flying (endo/exoskeletons)