Evolution and importance of plants

Question 1

What are defining characteristics of plants?

Answer 1

Plants are multicellular autotrophs that have alternation of generations (diploid and haploid orgs)

Question 2

What do we mean by “multicellular”?

Answer 2

Plants have more than just a colony a cells. They have specialized cells, differentiated by expressing diff sets of genes, that form tissues (dermal, ground, vascular such as xylem and phloem, leaves, flowers, roots)

Question 3

What is an “autotroph”?

Answer 3

self-feeding organism, plants make all organic molecules they need

Question 4

What do plants need to survive?

Answer 4

Water, CO2, sunlight, and a few minerals

Question 5

What is the exception to the term “multicellular autotrophs”?

Answer 5

Carnivorous plants

Question 6

What is alternation of generations? Describe the 2 phases

Answer 6

Plants alternate between a diploid org and a haploid org
During the gametophyte phase, meiosis occurs and haploid spores become gametophytes (1n) and then gametes (1n) after mitosis.
In the sporophyte phase, fertilization of the haploid gametes occur and zygotes form (diploid) and then become sporophytes (2n) which make spores through meiosis

Question 7

Examples of gametophyte and sporophyte

Answer 7

mosses = 1n (gametophytes) and trees/ flowering plants = 2n (sporophytes)
Note: sporophytes from from gametophytes!

Question 8

Why was the greening of the earth important?

Answer 8

it led to a major boom in diversity in plants and then animals

Question 9

What is the origin of plants?

Answer 9

About a million years ago a heterotrophic eukaryotic cell engulfed a cyanobacteria, which evolved into the modern-day chloroplasts (secondary endosymbiosis)

Question 10

Did plants evolve the ability to do photosynthesis?

Answer 10

No, cyanobacteria did

Question 11

Why were green algae important in the evolution of plants?

Answer 11

algae used photosynthesis which produced oxygen, ultimately leading the the development of the ozone layer, aerobic respiration in organisms, and therefore sustainable life on earth and eventually animals.

Question 12

what did modern plants evolve from?

Answer 12

green algae

Question 13

what are the similarities between modern plants and green algae?

Answer 13

same chlorophyll pigments and both have chloroplasts with thylakoids.

Question 14

What are the major evolutionary innovations of plants? (got plants from water to land)

Answer 14

Leaves, cuticles, stomata, guard cells, roots, vascular tissues, and lignin

Question 15

Leaves purpose

Answer 15

increase surface area for photosynthesis

Question 16

Cuticle function

Answer 16

waxy covering over the leaves that prevents water loss

Question 17

stomata

Answer 17

small opening on the underside of leaves used to regulate water movement through the plant

Question 18

guard cells

Answer 18

surround the stomata and help regulate water loss

Question 19

roots

Answer 19

anchors the plant to soil and absorbs nutrients –> necessary to live on land

Question 20

vascular tissue

Answer 20

transports water, mins, and metabolites throughout the plant (Xylem and Phloem)

Question 21

lignin

Answer 21

structural proteins in cell wall used for support (allows plants to be tall)

Question 22

Describe the first land plants

Answer 22

first plants were small (b/c lack of lignin) and show evidence of a cuticle to prevent desiccation (drying out) and the spores were likely surrounded by sporopollenin, a protective waxy covering, and found in sporangia

Question 23

What evolutionary innovation allowed for forests to spread?

Answer 23

roots because they helped create soil further aiding the spread of forests

Question 24

describe the carboniferous period

Answer 24

swampy, tropical forests made up of vascular plants covered much of the Earth, and photosynthesis caused a significant increase in oxygen levels and reduced the atmospheric CO2, the avg. temp was higher until the beginning of the Permian 299mya when the earth cooled

Question 25

What drove the evolution of seed plants

Answer 25

Seed plants evolved in response to cooling of earth and collapse of carboniferous rainforests

Question 26

what were the first seed plants?

Answer 26

gymnosperms which adapted seeds and pollen for drier environments
includes conifers (pine trees, cedars, junipers) and resulted in domination of coniferous forests for over 100 million years

Question 27

what is one of the most important evolutionary achievements to the number of different species on earth?

Answer 27

evolution of flowering plants which triggered a high rate of diversification in both plants and animals

Question 28

Order of evolution of plants

Answer 28

green algae –> cuticle, multicellular gametangia and embryos (nonvascular bryophytes)–> dominant sporophyte and vascular tissue (vascular seedless plants) –> seeds (vascular seed plants)

Question 29

Evolutionary importance of plants

Answer 29

add oxygen to atmosphere, making evolution of animals possible

Question 30

plants role in ecological complexity

Answer 30

ancient marine ecosystems (starting 1 billions yrs ago) developed multicellularity and provided additional nutrients, energy, habitats, and niches for other orgs
Later, terrestrial ecosystems (starting about 475 million yrs ago) and the first forests helped stabilize soil through their roots and created new niches and habitats for life on land leading to more animal diversity

Question 31

plants role in climate

Answer 31

plants caused global cooling over millions of years by removing CO2 from air, leading to evolution of first seed plant in response to cooler and drier climates

Question 32

plants role in diversity of animals

Answer 32

diversity gives rise to diversity –> coevolution -first flowering plants evolved to attract pollinators and then evolved fruits surrounding seeds to help with dispersal –> predators evolved (spiders, other, insects)

Question 33

the importance of photosynthesis

Answer 33

plants make nutrients and energy available to terrestrial and most marine ecosystems (all carbon and energy we have was made available to us by plants)
–> plants are important for nutrient and water cycling

Question 34

why does clearcutting rainforest negatively impact ecosystems?

Answer 34

leads to loss of habitats, soil erosion and loss of nutrients, and changes to local climate (makes them warmer and drier) due to reducing rates of transpiration

Question 35

importance of plants to civilization

Answer 35

plants provide food, building materials, medicines, herbs and spices, fiber, an nature makes us happy:)

Question 36

What must plants do to be multicellular autotrophs?

Answer 36

The must be self-feeding and have many different cell types that form different tissues