Algae vs Plants

What characteristics do plants and algae share?

• Both oxygen-producing photosynthetic autotrophs

• Some seaweeds look a lot like plants

• Some plants are mistaken for algae

• Plants and some algae belong to the same supergroup (evolved from a common ancestor)

What organisms belong to the Archaeplastida supergroup?

• Red algae

• Green algae

• Glaucophyte algae

• Plants

What are the embryophytes?

• Includes vascular plants and bryophytes

• Organisms thought of as “plants”

• Only group in the Archaeplastida lineage that are not algae

• Share characteristics with green algae, such as photosynthetic pigments

What separates the Embryophytes from algae?

• Algae lack the complex body form, reproductive structures, and adaptations to life on land found in many Embryophytes

• Example: desiccation-tolerant seeds, vascular tissues, and gas-exchanging stomata are found in many Embryophytes and are not present in most algae

What is one key feature that sets Embryophytes apart from their algal relatives?

• The development of a multicellular embryo that is nourished by the parent plant

• In many land plants, embryos develop into seeds within specialized reproductive tissues (flowers, cones, or fruits)

What are bryophytes?

• Mosses, liverworts, and hornworts

• The Embryophytes that are most closely related to green algae

• Lack true roots, stems, leaves, and a vascular system for transporting fluids

• Form embryos that are retained in the archegonium of the parent plant

What are charophytes?

The green algae that are most closely related to the Embryophytes

What are the dominant forms in Charophytes?

Haploid individuals

Where do embryos develop in Charophytes?

• Eggs and sperm are produced in oogonia and antheridia located on the same individual

• The fertilized egg (zygote) is released into the water

• It undergoes meiosis, and development of the next haploid alga occurs away from maternal tissues

Which supergroup do the seaweeds that display the greatest organ, tissue, and cellular specialization belong to?

SAR supergroup

How are brown seaweeds simpler than plants with fewer specialized cell types?

• Photosynthesis, gas exchange, and nutrient uptake is not restricted to specialized cell types found in plant leaves and roots

• These processes generally occur in cells located throughout the body of the alga

What is the function of fronds?

• Have specialized reproductive cells that produce haploid spores

• Do not have structures like stomata on plant leaves that are specialized for gas exchange

What is the function of the holdfast?

• Attaches the seaweed to the seafloor

• Not specialized to take up nutrients or water like the roots found in land plants

What is an example of parallel evolution between algae and plants?

Transport cells found in kelp stipes look a lot like the sieve elements found in vascular plants, but brown algae and plants belong to different eukaryotic supergroups and are not related to one another

How do embryos develop in brown seaweeds?

In contrast to plants, seaweeds typically release propagules into the water and subsequent development generally occurs independently of the parent

What are sori?

Dark patches on Bull Kelp blades where haploid spores are produced

How do embryos develop in Bull Kelp?

• Spores are produced in sori on the fronds and released directly into the seawater

• Haploid gametophytes develop from spores

How do embryos develop in Fucus sp.?

• Haploid eggs and sperm are produced in sexually mature fronds

• Fertilization occurs either in the fronds or in the seawater, depending on whether the species is monoecious or dioecious

• Early development occurs in the seawater, free from any maternal tissues