bio94 midterm 3 emerson

What are fungi?

More closely related to Animals than

plants.

- Both have DNA that sequences data

- Both synthesize chitin

- Flagella in chytrid spores and

gametes are similar to animal

flagella

- Animals and fungi store glucose as

the polysaccharide glycogen

Why are fungi important?

Acts as nutrient collectors for other plants, helps break down gut microbes, and plays a key role in nutrient cycling in ecosystems.

What are the 2 growths of fungi form?

Yeast and Hyphae

Yeast

- Single-celled fungi

- Reproduce by budding or fission,

found in environments like the human

body, soil, and fermented foods

Hyphae

Molds/Filamentous Fungi

Multicellular fungi

- grow as thread-like structures

(hyphae), forming a mycelium network,

essential for decomposition and

symbiosis with plants.

Mycelium

A network of interconnected hyphae

that forms the main body of a

fungus, often found underground or

within its food source

- Mycelia = plural form

Septa

Internal cross-walls within

hyphae that divide them

into compartments,

sometimes with pores to

allow the exchange of

nutrients and cytoplasm

Coenocytic fungi

lack a septa

What are the key features of chyrids?(Motile Fungi)

Only fungi with flagellated, swimming gametes and spores

What are the key features of Zygomycetes (Zygote Fungi)?

Forms tough zygosporanium during sexual reproduction

What are the key features of Basidiomycetes (Club Fungi)

Dikaryotic hyphae produce basidia inside mushrooms

What are the key features of Ascomycetes (Sac Fungi)

Form reproductive asci at hyphal tips

Reproductive structure of Chytrids

Gametangia(produces gametes), Sporangium(produces spores)

Reproductive structure of Zygoycetes

Zygosporangia(sexual) Sporangia (asexual)

Reproductive structure of Basidiomycetes

Basidia (Club like spore porducing cells)

Reproductive structure of Ascomycetes

Asci (sac-like spore producing cells)

Spore characteristics of Chytrids

Haploid swimming spores and gametes w flagella

Spore characteristics of Zygoycetes

Haploid spores produced via mitosis in sporangia

Spore characteristics of Basidiomycetes

Each Basidium produces four spores

Spore characteristics of Ascomycetes

Each ascus produces eight spores

Mode of dispursal Chytrids

Water (spores swim)

Mode of dispersal Zygoycetes

Wind dispersal

Mode of dispursal Basidiomycetes

Wind Dispersal

Mode of dispursal Ascomycetes

Forceful ejection of spores

Symbiosis

Any relationship in which two species live closely together

Mutualism

Both species benefit

Parasitism

One species benifits, the other is harmed

Commensalism

one species benefits the other is unaffected

Ectomycorrihizal Fungi (EMF)

Symbiotic organisms that form partnerships with tree roots, primarily in temperate and boreal forests. They create a sheath around root tips and exchange nutrients with the host plant. These fungi improve plant nutrient uptake, soil structure, and forest ecosystem health. They include many edible mushroom species and play a crucial role in forest ecology and carbon cycling.

Arbuscular Fungi (AMF)

symbiotic fungi that form associations with the roots of about 80% of land plant species. They penetrate plant root cells, forming tree-like structures called arbuscules. AMF helps plants absorb nutrients, especially phosphorus, from the soil. In return, they receive carbohydrates from the plant. These fungi are important for plant nutrition, soil structure, and ecosystem functioning in many terrestrial habitats, including agricultural systems.

Why are fungi good decomposers?

● Large surface area of a mycelium makes nutrient absorption is exceptionally efficient

- Useful in nutrient-poor environments

Key characteristics of saprophytic fungi

1. Grow toward dead tissues for food

2. Secrete digestive enzymes to break down complex organic matter

3. Recycle nutrients back into the ecosystem

Key facts about animals

1. Multicellular eukaryotes with extensive extracellular matrix (ECM)

2. Heterotrophs

3. All animals except sponges have:

   • Neurons for transmitting electrical signals

   • Muscle cells for body shape changes through contraction

Porifera (Sponges)

1. Earliest animals in fossil record (hypothesized)

2. Lack complex tissue

3. Some have true epithelium:

   • Tightly joined cells covering interior and exterior surfaces

   • Essential feature

Choanoflagellates

1. Single-celled aquatic eukaryotes

2. Closest living relatives to animals

3. Collar of microvilli around flagellum

4. Can be unicellular or colonial

5. Feed on bacteria and small particles

6. Marine and freshwater habitats

7. Share many genes with animals

8. Important for understanding animal evolution

Triploblast

3 germ layers

- Ectoderm: Outer covering & nervous

system

- Endoderm: Digestive tract lining &

associated organs

- Mesoderm: Muscles, circulatory

system, bones, and most internal

organs

Bilateral symmetry

1. Body divided into mirror-image left and right halves

2. Anterior (head) and posterior (tail) ends

3. Dorsal (back) and ventral (belly) sides

4. Enables streamlined movement and cephalization

5. Common in most animals (humans, insects, fish)

6. Evolved in Cambrian period

7. Allows for complex body plans and behaviors

Diploblast

2 germ layers

- Ectoderm: Outer covering &

nervous system

- Endoderm: Digestive tract

lining & associated organs

Radial symmetry

Body parts around central axis

1. No distinct front/back

2. Examples: jellyfish, starfish

3. Suited for sessile/slow-moving organisms

4. Common in aquatic environments

5. Limits directional movement

Symmetry

Symmetry in bilaterians results from action of Hox genes and Decapentaplegic (dpp) genes:

Hox genes

Regulate development of the dorsal–ventral axis

Protostomes

named for embryonic development of mouth before anus

Deuterostomes

named for embryonic development of anus before mouth

The importance of segmentation

● Structural Organization:

- Helps categorize animals based on body plan and modular body

organization

- Ex: Segmented backbone = vertebrates

● Functional Adaptation:

- Allows for specialization of body parts, leading to increased

efficiency in movement, feeding, and reproduction

- Tool-kit gene

- Different environments lead to diversification due to a change in

body structure

Protostome development

○ Embryonic development of

mouth before anus during

gastrulation

○ Inability of isolated embryonic

cells to develop into complete

embryo

○ Formation of coelom by splitting

of blocks of mesodermal cells

Water to land transitions

Protostome lineages originated in the

ocean

● Transitions to aquatic → terrestrial

environments occurred multiple times

● Transition to land coincided with

adaptive radiation of plants on land

New adaptations had to ensure that

protostomes were able to exchange

gases, avoid drying out, and hold up

their bodies under their own weight

Roundworms and earthworms:

○ Developed a high surface area to

volume ratio

○ Increases efficiency of gas

exchange across their body

surface in their moist

environments

Arthropods and mollusks

○ Developed gills or other

respiratory structures located

inside of the body

○ Minimizes water loss when

moving to land

○ Compartmentalized body plans

→ body divided into different

regions with different functions

Insects

○ Waxy layer → minimizes water loss

from body surface

○ If environment dries, openings to

respiratory passages can be closed

○ Desiccation-resistant eggs → insect

eggs have thick membrane that

maintains moisture

Lophotrochozoans

If an animal has the following three

characteristics, it must be a

lophotrochozoan:

○ Lophophore (feeding structure -

suspension feeding)

○ Trochophore (larvae)

○ Spiral pattern of cleavage

● Examples: rodifera, mollusca, annelida

Mollusca

○ Gastropods (ex. snails)

○ Bivalve (ex. clams)

○ Cephalopods (ex. octopus)

Visceral mass

contains all main

internal organs and external gills

→ helps them breath

Radula

tongue (unique to mollusks!)

Hemocoel

body cavity, not lined in mesoderm (not a coelom), body fluids bathe organs directly

Shell

used for defense protection, armor

Mantle

secrets a shell made of calcium

carbonate - many adaptations of mantle

→ diverse functions!!

Mantle examples

○ Terrestrial snails: mantle forms internal

lung

○ Bivalves: mantle is lined with muscle and

forms tubes called siphones

○ Cephalopods: mantle forms siphon that

functions in jet propulsions

Annelids

Wormlike, Has coelom, Fully developed digestive tract with mouth, anus, and segmented body

Flatworms

Broad, flat shaped bodies

○ Large surface area for gas

exchange

○ Nutrients and gases to diffuses

efficiently to cells

● Reside in moist/aquatic environments

● Lack coelom and structures specialized

for gas exchange

Mollusca

a phylum of segmented worms

Ecdysozoans

● Cuticle and exoskeleton → structure

for muscle attachment + protection

from predators

● Molts frequently, uses hormone called

endysone to regulate molting cycle

● Once organism molts, fluid causes

body to expand and newer, larger

cuticle/exoskeleton forms

Arthropods

● Most important phylum in Ecdysozoa

○ Most abundant and diverse

duration in the fossil record!

● In aquatic and terrestrial

environments

● Four main lineages:

○ Myriapods (eg. centipedes)

○ Insects (eg. ladybugs)

○ Crustacean (eg. shrimp)

○ Chelicerates (eg. spiders)

Incomplete metamorphosis

(hemimetabolous)

○ Form of direct development

○ Nymphs (juveniles) look like smaller

version of adult

Complete metamorphosis

(holometabolous)

○ DISTINCT larval stage!

○ Larva becomes pupa

○ Pupas body completely remodeled

into new adult form

Roundworms

○ Unsegmented worm with no

appendages

○ Tube within-a-tube body plan

○ Pseudocoelom

Echinoderms

Three Primary Synapomorphies:

1. Radial Symmetry in adults

2. Endoskeleton of Calcium

Carbonate

3. Water Vascular System

all r marine animals

Chordates

Four Synapomorphies:

1. Pharyngeal slits/pouches

2. Dorsal hollow nerve cord

3. Notochord

4. Muscular post-anal tail

Three “Subphyla” of chordates:

1. Cephalochordates

2. Urochordates

3. Vertebrates

*Cephalochordates and Urochordates

are not super important*

Order of Evolution in Vertebrates

1. Jawless fish

2. Amphibians

3. Reptiles

4. Birds

5. Mammals

Jawless fishes

Earliest known vertebrates!

All the four features of chordates plus

two extra!

1. Cranium

2. Column of Vertebrae

First instances of specialized neural

crest cells other neural formations

Jawed Fishes (Gnathostomes)

4 Major Lineages:

1. Cartilaginous Fish

2. Ray Finned Fish

3. Coelacanths

4. Lungfishes

Formation of the tetrapods

Three main lineages:

1. Amphibians

2. Reptiles/Birds

3. Mammals

Amphibians

Lay eggs in the water

● Juveniles develop in water

Adults live on land

Gas exchange via skin

● Development of lungs!

Undergo metamorphosis!

Amniotic Eggs: Moving Eggs to Land

Survive on land

• All tetrapod eggs EXCEPT amphibians

• Three membranes:

1. Embryo

2. Yolk

3. Waste • Found in: Reptiles and Mammals

Reptiles

Second major lineage of amniotes other

than mammals

● Amniotes that are NOT mammals

Four Major Types:

1. Lizards and Snakes

2. Turtles

3. Crocodiles and Alligators

4. BIRDS!

Lizards, Turtles, Snakes and Crocs

Evolved from Amphibians

● Water eggs → Amniotic Eggs

Scaly Skin

● Lightweight protection

Lay Amniotic Eggs

Ectothermic

● Need outside heat to regulate

temperature

Birds

Technically reptiles

● Fit into the definition of a reptile

Differences from reptiles:

1. Have feathers

2. Endothermic

Evolved from feathered dinosaurs!

Mammals

Group of organisms that can produce

milk for their young!

● Mammary Glands

○ Presence of cheek muscles

and lips as well!

Also have fur/hair to help insulate them

● Endothermic!

Extensive Parental Care

Types of Mammals

1. Monotremes

2. Marsupials

3. Placental Mammals

Monotremes

Mammals that lay eggs and nourish their young with milk

Marsupials

Mammals that nourish their young in an abdominal pouch

Placental Mammals

Mammals that develop in the uterus and are not stored in an abdominal

pouch

Types of Reproduction

Oviparity, Viviparity, Ovoviviparity

Oviparity

Lay external eggs that then hatch

Viviparity

Develop the young inside the body without any egg → Live birth

Ovoviviparity:

Egg is retained inside the mother, where it hatches and then is

released later

Advantages of the placenta:

● Constant temperature

● Protected

● Portable

Downside of the placenta:

● Expensive to produce

● Costly and dangerous

Primates

diverse order of mammals

Major Groups:

1. Prosimians

2. Anthropoids

3. Hominoids

Prosimians

1. Small Bodied

2. Arboreal (Lives in Trees)

3. Nocturnal

Branched off from from Anthropoidea

● Include lemurs, tarsiers, pottos and

lorises

Form a paraphyletic group

subgroup of primates

Anthropoids

“Human-like” Monkeys

● New World Monkeys, Old World

Monkeys, Gibbons and Hominoids

(Great Apes)

Paraphyletic Group

Hominoids

apes

● Large bodies with long arms and

short legs

● No tail!

● Knuckle-Walking

○ Humans are the only bipedal

great ape!

Hominins (Humans)

Four main types:

1. Gracile Australopithecines

2. Robust Australopithecines

3. Early Homo

4. Recent Homo

Only Homo Sapiens Survived...

Gracile vs. Robust Australopithecines

Gracile Australopithecines: • Slender build • Most likely bipedal

Robust Australopithecines: • Stockier than gracile • Broader, more robust build • Large cheekbones and jaws • Strong chewing power

Early vs. Recent Homo

Homo = Humans (Homo _____ = type of human)

Compared to Australopithecines: • Flatter, narrower faces • Smaller jaws and teeth • Larger braincases

Recent Homo vs. Early Homo: • Above traits more prevalent

Key species: Homo sapiens

Important concept: Out-of-Africa Theory

Out-of-Africa Theory

1. Homo sapiens originated in Africa

2. ~200,000-300,000 years ago

3. Left Africa ~50,000-70,000 years ago

4. Spread globally, replacing earlier hominids

5. Supported by genetics, fossils, archaeology

6. All non-Africans descend from these migrants

7. Opposes multiregional hypothesis

Lophotrochozoans

1. Protostome superphylum

2. Lophophore or trochophore larvae

3. Major phyla: Mollusca, Annelida, Brachiopoda, Nemertea

4. Diverse body plans and habitats

5. Mostly marine, some freshwater/terrestrial

6. Ecologically important

EMF vs AMF

EMF form external sheaths; AMF form internal structures • EMF associate with fewer plant species; AMF with most land plants • EMF dominant in temperate forests; AMF more widespread globally