final exam week 8-12 bio153 Flashcards
1
Q
what is the main difference between algae and plants?
A
pthe similarities between algae and plants are:
1. both are eukaryotic photoautotrophs (perform photosynthesis)
2. both can be multicellular (all plants are, many alge too
alternation of generations occur in both (all plants, many algae)
both have plastids from cyanobacteria (via endosymbioisis)
both have cellulose based cell walls
( in all plants and many algae, example being brown algae and charophytes)
the key difference sbetween the two are:
plants live on land and algae are entirely aquatic.
2
Q
why is living on land beneficial for plants?
A
Easier access to sunlight (less absorption than in water)
Better access to soil nutrients
Less competition for light in early land environments
3
Q
how does water affect sunlight absorption compared to land?
A
Earth’s atmosphere is 50 km thick, and 50% of sunlight reaches the surface
Once in water, 50% of sunlight is absorbed in the first 10 meters
This limits photosynthesis for aquatic organisms like algae
4
Q
what are the challanges plants face on land?
A
Less water for photosynthesis
Risk of desiccation (drying out)
No structural support from water (gravity)
No water for sperm/spore mobility
5
Q
what adaptations allow plants to survive on land?
A
Leaves: capture sunlight and CO₂
Roots: absorb water and minerals
Vascular system: xylem (water), phloem (sugars)
Cuticle: waxy coating to prevent desiccation
Stomata: gas exchange, can close in dry conditions
Pollen: protects sperm and allows dispersal without water
Seeds: package embryos with food and protection
6
Q
what are the key evolutionary steps in land plant development?
A
Step 1, mosses: basic traits to persist on land
Step 2: ferns, traits to combat gravity
Step 3, pines, traits to reproduce without water
Step 4, flowers, traits to take full advantage of terrestrial environment
During this process, the alternation of generation changed from gametophyte dominated cycle to an extremely sporophyte dominated cycle~
About 90% of plant species are angiosperms, showing how successful their strategy is to occupy diverse niches on land. Other plants are also competitive and effective, like a pine forest, but not as diverse!
7
Q
what traits help mosses survive on land? (desseciation)
A
Sporopollenin: protects spores from desiccation by covering spores
Cuticle: waxy coating to reduce water loss all over plant body (different from animal cuticle)
Stomata: regulate gas exchange (o2 and co2 exchange and close in dry conditions)
and water retention
8
Q
why dont mosses grow tall?
A
No hardened tissues for support (for support against gravity)
No vascular system for water/nutrient transport
Use rhizoids to anchor, not absorb water
Must absorb water directly from environment
9
Q
what is a moss gametohpyte, moss sporophyte, and the sporangium
A
moss gamtophyte is what we see as the green, mossy, thing we typically think of as “moss”
moss sporophyte is the appendages which grow out from the gametophyte
the moss sporophyte has sporangium which is spore producing tissue at the end
- completely dependent on gametophyte for growth and sruvival and usually has a shorter life than the gametophyte.
10
Q
what characterizes the moss life cycle?
A
Moss spores grow into protonemata
Protonemata produces buds which grows into full female or male gametophyte
Male gametophyte produce sperms, female gametophyte produce eggs
Flagellated sperms swim to eggs
Fertilized zygote grows into sporophyte
While being nurtured by female gametophyte
They mature sporophyte released spores while still being attached to the female gametophyte.
11
Q
what do mosses depend on and why do they still depend on it?
A
The moss life cycle depends on water
Fertilization depends on water since sperm need to swim through water to reach the egg
The absence of vascular tissue means all parts of moss gametophyte needs to directly absorb water from the environment
Mosses usually grow in humid and moist habitats for that reason.
Moss protonemata looks very similar to charophyte algae
Sperm are flagellated and must swim to egg
No vascular tissue, so all cells absorb water directly
Found in moist habitats
Protonemata resemble charophyte algae
12
Q
how are ferns more advanced than mosses
A
Have true roots, stems, and leaves
Vascular system with xylem and phloem
Taller growth for better light access and spore dispersal
Do not need direct wetness to acquire water
13
Q
what does the vascular system do in ferns
A
Xylem: transports water & minerals, dead at maturity, strengthened by lignin
Phloem: transports sugars and other nutrients
Allows internal water transport; leaves can stay dry due to refcieving water through the vascular system
14
Q
what are sporophylls and sporangia in ferns
A
Sporophyll (plural, sporophylls) are leaves of vascular plants which have been modified to produce spores
Sporangium (plural sporangia) are reproductive tissue located on the sporophyll which actually produce the spores
“sporophytes have leaves, some leaves are sporophylls. sporophylls produce sporangia and the sporangia produce spores”
15
Q
what is the fern life cycle and is it sporophyte or gametophyte dominated
A
sporophyte dominated
Spores grow into bisexual gametophyte
Gametophyte produces both the sperm producing organ and the egg producing organ. Sperm swims through moisture to reach the egg.
Fertilization of egg by sperm to produce the zygote
Zygote develops into sporophyte while it is supported by the gametophyte
Mature sporophyte is independent from the parental gametophyte. It produces spores from sporangia
(use picture for help!)
16
Q
hw do fern gametophytes and sporophytes differ
A
Fern gametophyte is much smaller than the sporophyte
- it is independently body capable of photosynthesis
Fern sperms swim to the egg for fertilization
Fern sporophytes do not require complete wetness to acquire water for photosynthesis
However, fern gametophytes still depend on water for fertilization.
17
Q
what are gymnosperms
A
Gymnosperms are seed-forming, non-flowering plants (e.g., pines, cycads). They reproduce without water using pollen and seeds.
18
Q
how do gymnosperms reproduce wihtout water?
A
Pollen contains the male gametophyte + sperm and is dispersed by wind or animals
Seeds are sporophyte embryos in a hard shell with food, also dispersed by wind or animals
19
Q
what are cones in gymnosperms?
A
Cones = scaly gymnosperm sporophylls (leaf structures that produce spores)
Microcones (male) produce pollen
Megacones (female) house ovules
20
Q
describe the male gymnosperm reproductive process
A
Microsporophylls (2n) contain microsporangia (2n)
Microsporangia make microspores (n) by meiosis
Microspores become male gametophytes (n) → make sperm (n)
Packaged into pollen → dispersed by wind
21
Q
describe the female gymnosperm reporductive process
A
Megasporophylls (2n) contain megasporangia (2n)
Megasporangia make megaspores (n) by meiosis
Megaspore becomes female gametophyte (n) → makes egg (n)
All enclosed in the integument → forms the ovule
22
Q
what is an ovule in gymnosperms
A
Ovule = integument + megasporangium + megaspore After pollen grain attaches to the ovule (pollination), the pollen tube delivers sperm to
the egg to produce the zygote (fertilization).
* The zygote grows into the embryo, which is the ‘baby’ form of the new sporophyte
* Other tissues of the female gametophyte becomes the food supply, packaged into seed
* Integument becomes the seed coat
6
Figure 30.3 modified
* Gymnosperm has an extremely sporophyte-dominated life cycle
* Both gametophytes are microscopic bodies which is held within the large sporophyte body
23
Q
what happens after pollination in gymnosperms
A
Pollen grain lands on ovule
Pollen tube delivers sperm to egg → fertilization
Zygote forms → becomes embryo
Female gametophyte becomes food supply
Integument becomes seed coat
24
Q
whats the major difference between gynosperms and angiosperms?
A
Gymnosperms: “Naked seed” (ovule exposed)
Angiosperms: “Container seed” (ovule enclosed in ovary → becomes fruit)
25
what advantages did flowers and fruits give angiosperms
Enabled animal pollination
More efficient dispersal via wind or animals
Allowed angiosperms to dominate land ecosystems
26
what are the parts of a flower and their functions?
sepal: base of the flower, protects flower before it opens
Petal: Attracts pollinators
Stamen: Male organ
Anther: Has microsporangia (makes pollen)
Filament: Holds anther
Carpel: Female organ
Stigma: Catches pollen
Style: Connects stigma to ovary
Ovary: Contains ovules (each = integument + megasporangium + megaspore)
directly from lecture:
Photographed by Ichiro @ UTM Campus
Angiosperms: Take full advantage of terrestrial environment
* Angiosperms are seed-forming, flower- and
fruit-forming plants
* Development of flowers and fruits allowed
angiosperm to take full advantage of the
terrestrial environment (such as animals)
* Some pollens and seeds (fruits) specialized
for dispersal by animals
* Other pollens and seeds (fruits) specialized
for more efficient dispersal by wind
10
Image credits at end of slides
Taraxacum officinale, the common dandelion
Dandelion
Flowers
Dandelion fruits (with seeds
attached to the ends)
Flower makes animals help pollination
* Unique structure to facilitate pollination
via animals
* Sepal: base of the flower, encloses the
flower before it opens
* Petal: brightly coloured portion of the
flower to attract pollinators
* Some flowers are wind pollinated
11
Figure 30.9
Simplified diagram of a 'flower'
* Many flowers have a more complicated configuration
Flower makes animals help pollination
* Stamen: male reproductive organ
* Anther contains microsporangia to produce
pollens
* Filament is the supportive structure with
anther on its end
* Carpel: female reproductive organ
* Stigma is the sticky tip of carpel to capture
pollens
* Style connects the stigma to the ovary
* Ovary is the base of carpel that contains the
ovules
* Ovule = integument + megasporangia +
megaspore
* Angiosperm ovules are contained in the ovary
27
how oes pollination and fertilization work in angiosperms?
Pollen lands on stigma → pollen tube grows toward ovule
Sperm delivered to egg → fertilization
Ovule becomes seed, ovary becomes fruit
28
what is the angiosperm life cycle?
Megasporangium in each ovule produces megaspore. Megaspores grow into female gametophyte which produces egg
Microsporangium in the anther produces microspores
Microspores develop into male gametophytes, which get packaged into pollen alongside its sperm. Pollen gets delivered to stigma (pollinization) and pollen tube begins to grow
Pollen tube reaches the ovary and delivers sperm to the ovule
Fertilization of egg and sperm into zygote
Zygote develops into the embryo. Other parts of the ovule develop into the seed. The ovary develops into the fruit
Seed gets dispersed and grows into mature plant (sporophyte)
29
how did flower diversity evolve?
Through adaptation to animal pollinators
Some flowers bred by humans for color/shape
30
31
how do fruits facilitate the dispersal of seeds?
Fruits develop from ovaries to usually encase the seed.
This protects the seed and helps with dispersal
Fruits can be fleshy or dry (like tomatoes plums and grapes being fleshy and beans nuts and grains of rice being dry)
Some fruits get dispersed by animals. Eaten by animals then the undigested seed gets released with the feces. Sometimes it's stored underground by animals that forget it and sticks onto animals to get carried around too!
Some fruits are specialized for wind dispersal! For example, dandelion fruit and the maple fruit which have a wing like structure to glideee throughout the wind!
32
what are the types of fruit?
1. Simple Fruit
🍐 Example: Pea
Comes from 1 carpel or fused carpels in a single flower.
Other examples: cherry, tomato, peach.
2. Aggregate Fruit
🍇 Example: Raspberry
Develops from one flower with many separate carpels.
Each tiny bump on the raspberry is a fruitlet from its own carpel.
Other examples: blackberry, strawberry.
3. Multiple Fruit
🍍 Example: Pineapple
Forms from many flowers whose ovaries fuse into one big fruit.
Each segment of a pineapple was originally a flower!
Other examples: figs, mulberries.
4. Accessory Fruit
🍎 Example: Apple
Fruit includes parts other than the ovary — like the receptacle (the base of the flower).
The core is the actual fruit; the fleshy part we eat is accessory tissue.
Other examples: strawberry (the red part is accessory!).
33
whats special about dandelions
Dandelion flower = many florets (each sead head contains about 40-100 florets)
Each fruit = 1 seed + wings (pappus) → wind-dispersed
Seed head = cluster of many individual fruits
34
what are the functions of roots?
Anchor plant
Absorb water and minerals
Store carbs (e.g., carrots = root veggies)
Sometimes specialized (e.g., tubers like potatoes store food)
35
how do plants absorb nitrogen?
:
Absorb mainly nitrate (NO₃⁻) and some ammonium (NH₄⁺)
Nitrogen-fixing bacteria in soil convert N₂ gas → ammonia (NH₃) → ammonium
some of these nirogen fixing bacteria are free living and other forms of symbiotic rleationships with certain types of plants
36
what occurs in the nitrogen cycle
Bacteria of rhizzobium sp. Coexist inside specialized root nodules of their host plant.
Growing plant invite rhizobium sp to infect their root, while the bacteria also emits chemical sto facilitate the process
The infected area develops into nodules for rhizobium to live inside
A vascular system is established between the nodule and root for nutrient exchange
Nodule provides an anaerobic environment for rhizobium to fix nitrogen
Plant also provides other nutrients to keep rhizobia population healthy
Rhizobium provides the plant with fixed nitrogen
Many species of legume plants can form this mutualistic relationship like beans, lentils, chickpeas, alfalfa, clover…
🌱 What is Rhizobium?
Rhizobium is a type of bacteria that lives in the soil.
It has a special ability: it can "fix" nitrogen — turning nitrogen gas (N₂) from the air into a form that plants can use (like ammonia).
🟢 How does this partnership work?
1. Plant invites Rhizobium
When a legume plant (like beans, lentils, or clover) is growing in nitrogen-poor soil, it releases chemicals from its roots to attract Rhizobium bacteria.
At the same time, Rhizobium bacteria release their own chemicals to communicate with the plant.
2. Infection and Nodule Formation
Rhizobium enters the plant's root through small hairs.
The root becomes infected in a controlled way and starts to swell, forming a nodule (a small bump).
This nodule becomes Rhizobium’s home.
3. Vascular Connection
Inside the nodule, the plant creates a vascular system — basically a transport system to exchange nutrients between the plant and the bacteria.
🧪 What does each side give?
🌬️ Plant gives Rhizobium:
An anaerobic (no oxygen) environment — because nitrogen fixation can’t happen if there’s too much oxygen.
Nutrients (like sugars) to keep the Rhizobium alive and active.
💨 Rhizobium gives the plant:
Fixed nitrogen, which the plant needs to grow — especially to build proteins and DNA.
This is super valuable because plants can’t use nitrogen gas directly from the air.
🤝 Mutualism:
This is a mutualistic relationship — both benefit:
The plant gets nitrogen (which is often in short supply in the soil).
The bacteria get a safe home and food.
37
crop rotation. what is it?
🌾 What is Crop Rotation?
Crop rotation is a farming method where different types of crops are planted in the same field in different seasons or years, instead of planting the same crop over and over again.
🚫 What happens with monocropping (same crop every year)?
Crops like wheat absorb lots of nitrogen from the soil.
If you keep planting wheat (or any one crop) in the same field year after year, it uses up the same nutrients—especially nitrogen.
This leads to soil nutrient depletion, which makes crops grow poorly over time.
It also increases pests and diseases, since they thrive when the same crop is always available.
🌱 How do legumes help?
Crops like beans, lentils, chickpeas, and clover are legumes.
Legumes form a mutualistic relationship with nitrogen-fixing bacteria (Rhizobium).
These bacteria live in root nodules and convert nitrogen gas (N₂) from the air into usable nitrogen in the soil.
This adds nitrogen back into the soil — basically, legumes "recharge" the soil.
🔄 How does crop rotation work?
Year 1: Plant a nitrogen-absorbing crop (like wheat or corn).
Year 2: Plant a legume (like lentils or alfalfa) to add nitrogen back.
Repeat: Alternate between nutrient-using crops and soil-enriching crops.
✅ Benefits of Crop Rotation:
🌿 Prevents soil nutrient depletion
🌾 Boosts crop yield naturally
💸 Reduces need for synthetic fertilizers
🐛 Disrupts pest and disease cycles
🌎 Promotes long-term soil health
🧠 Simple Summary:
Crop rotation alternates between nutrient-hungry crops and soil-restoring legumes to keep the soil healthy, increase yield, and reduce fertilizer use.
38
what is the three field crop rotation system?
First field: nitrogen depleting crops such as wheat/rye
Second field: legumes such as peas and beans
Third field: no crop planted. The field gets overgrown by weeds. Animals are grazed on this land to add more nutrients through their feces
Crop rotation drastically increases the amount of crop yield while reducing the need for artificial fertilizers. It was a key innovation for human society to sustain a high population
39
what defines the kingdom animalia (metazoa)
the kingdom animalia (metazoa) are:
Chemoheterotrophic hunters that internalize food for digestion
Multicellular eukaryotes (like plants and fungi)
Lack cell walls (unlike plants and fungi)
Use compounds like collagen for structural support
Life cycle is dominated by multicellular diploid adult phase (no multicellular haploid form)
40
how do animals differ from pkants and fungi in structure and nutrition?
Plants: photoautotrophs, fix CO₂ using water/sunlight
Fungi: chemoheterotrophs that externally digest food(chemoheterotrophic decomposers who digest food outside their body and absorb the nutrients)
Animals: chemoheterotrophs that digest food internally
Animals lack a cell wall; plants have cellulose, fungi have chitin
Animals use extracellular proteins like collagen for support
41
what key features define the animal body plan?
A digestive tract: a specialized bag inside the body for digesting food
Nearly all animals have a digestive tract (except a few like sponges)
42
what is the development process of the animal embryo?
an animal zygote intially divides by cleavage (cleavage is succession of mitotic cell division which is not accompanied by cell growth), basically "binary fission" without increase in body size
then forms a blastula which is a hollow ball of cells which is called the blastocoel
43
what is gastrulation and what layers does it form?
Gastrulation: part of development where one side of blastula folds inward
Forms the gastrula
Archenteron: Cavity inside the gastrula
* Blastopore: Opening into the cavity
Creates:
Ectoderm (outer layer, faces environment)
Endoderm (inner layer, lines archenteron cavity)
Blastopore: opening to the archenteron
Later forms the mesoderm (middle layer)
44
what does the second opening do and where does it occur
A second opening occurs in gastrula to complete the digestive tract
* The other end of the gastrula opens
to complete the digestive tract
* One opening becomes the mouth,
the other becomes the anus
* Exactly which opening becomes the
mouth/anus depends on the type of
organism
* Mesoderm: During this development,
a third layer of cells develop between
the endoderm and ectoderm
45
what are humans and what does our blastopore do?
humans are dueterostomes, our blastospore develops ino the anus, the second opening develops into the mouth
46
what tissues/organs come from each germ layer?
Ectoderm: skin, hair, nervous system, jaws, teeth, germ cells
Endoderm: linings of digestive, respiratory, excretory, reproductive tracts, liver
Mesoderm: skeleton, muscles, circulatory systems
Not all animals have a mesoderm (e.g., cnidarians)
47
what determines the mouth and anus in animals?
During development, the blastopore and a second opening form
Protostomes: blastopore becomes mouth
Deuterostomes (e.g., humans): blastopore becomes anus, second opening becomes mouth
48
how are identical twins formed in humans
Animal embryos (including humans) use indeterminate cleavage
cells at early embryonic stage are not completely fixated by their differentiation, and can still become a whole organism if seperated.
Early-stage cells can still develop into a full organism if separated
Monozygotic twins: single embryo splits into two
Dizygotic twins: two eggs fertilized at once
49
what is a body plan in animals
The fundamental layout or symmetry of the body:
Radial symmetry
Bilateral symmetry
No symmetry
50
what is radial symmetry and which aniamls have it
Body parts arranged around a central axis
Equal environmental interaction from all directions
Found in sessile (fixed) and planktonic (drifting) animals like jellyfish and sea anemones (like a starfish)
51
what is bilateral symmetry and its key features
Body has two axes:
Head-Tail (Cranial-Caudal)
Dorsal-Ventral (Back-Belly)
Divides body into left and right sides
Often includes central nervous system and sensory structures in the head (cephalization)
Seen in humans, dolphins, butterflies, etc.
52
what about animals with no symmetry?
Sponges: the most basal animals
Often grow into random shapes with no symmetry
Lack true tissues (e.g., muscle, nerve)
53
whats the evolutionary origin of animals
Animals (Metazoa) form a monophyletic clade
Sponges (Porifera) were the first to branch off
All other animals = Eumetazoa, which have true tissues
54
what are the major groups of eumetazoa
Basal Eumetazoans: radial symmetry (e.g., jellyfish)
Bilateria: bilateral symmetry
Three major clades:
Lophotrochozoa: snails, worms, squids
Ecdysozoa: insects, spiders, nematodes
Deuterostomia: humans, starfish
95% of animals = invertebrates
55
how do sponges feed and function?
Sedentary suspension feeders
Draw water through side pores, release from central cavity
Inner layer = choanocytes: beat flagella to create water flow and capture food
Amoebocytes: transport nutrients
Middle layer = mesohyl (gel-like matrix)
56
what are choanoflagellates their importance to animals?
Closest protist relatives of animals
Look almost identical to collar cells (choanocytes) in sponges
Share molecular similarities with animals
Present in animals but not in fungi/plants
57
whats special about salpingoeca rosetta?
A colonial choanoflagellate
Can stick together to form colonies (they have proteins that do that and form a colony)
Cells differentiate depending on environment (colonial individually swimming, etc)
Studied to understand origin of animal multicellularity
58
what are invertebrates
Animals without a vertebra (backbone)
Includes all animals except part of the phylum Chordata
Lack traits like backbones, hinged jaws, limbs with digits
Even some Chordates (e.g., lancelets) are invertebrates
59
what are characteristics of all eumetazoa (except select exceptions)
:
Have a digestive tract
Have differentiated tissues
Exhibit wide morphological diversity, especially in Lophotrochozoa and Ecdysozoa
Morphology alone is not reliable for ancestry—phylogeny is based on molecular data
60
what defines lophotrochozoa
Exclusively invertebrates
Some have:
Lophophore: a crown of ciliated tentacles used for feeding
Trochophore larva: a developmental stage
Many members lack these traits but are grouped based on molecular data
61
what animals are included in lophotrochozoa?
Flatworms (planarians, tapeworms)
Molluscs (snails, slugs, oysters, clams, octopus, squid)
Annelids (earthworms, leeches)
Known for extreme body plan diversity
62
what are molluscs and their key features?
Second most diverse animal phylum (after arthropods)
Mostly marine; some freshwater and terrestrial
Soft-bodied; many secrete calcium carbonate shells (may be internalized or lost)
63
what are the three main body parts of molluscs?
Foot – for movement and attachment
Visceral mass – houses internal organs
Mantle – covers visceral mass, secretes shell
Mantle may create a mantle cavity (open space with gills, anus, excretory organs)
64
what are bivivales and how do they feed?
Aquatic suspension feeders: clams, oysters, mussels, scallops
Have two shells hinged together (strong muscle(s) close them tightly
Use gills for respiration and feeding (gas exchange, water inhaled from incurrent siphon into the mantle cavity, and pumped out from the excurrent siphon) (gills trap food as water passes through gills)
Water flows in through incurrent siphon, out excurrent siphon
Low mobility, but some can swim by flapping valves
65
what are cephalopods and how do they move?
Predatory molluscs: octopus, squid (like the hawaiian bobtail squid, excurrent siphon is seen on the lower side, pair of flaps on the sides of mantle, used for gentler/finer movement
Mantle is external (on the outer surface, shells minimized, internalized or lost)
Shells are reduced, internalized, or absent
Draws water into the mantle cavity
through incurrent siphon
* Contracts mantle to release water jet from
the excurrent siphon, propelling the animal
* The muscular siphon can be pointed
towards different positions
Chromatophores help camouflage or signal
66
what defines ecdysozoa
Exclusively invertebrates
Have cuticle-based exoskeletons
Grow via ecdysis (molting)
The most species-rich group in Animalia (nematods, millipeds, centipedes, crustaceans, insects, etc.
contains more species than all other animal, protist, fungus, and plant groups combined! more species than all other eukaryotes combined!!
67
what groups are included in ecdysozoa?
Nematodes: roundworms (free-living and parasitic)
Arthropods: crustaceans, insects, centipedes, millipedes
68
what are nematods and what makes C.elegans important?
- worms found in many habitats like aquatic, soil, moist tissues of plants, body fluids and tissues of animals
- many are free living, other are parasitic (trichinella spiralis is the muscle burrowing parasite found in pork)
- Caenorhabditis elegans (C. elegans)
* An adult has 959 cells or 1033 cells depending on
gender
* The exact locations as well as their developmental
pathways for ALL cells has been mapped
* Model organism for biology in various
developmental- and medicinal fields of research
69
what are the key features of arthropods?
Crustaceans (crabs, lobster, etc.), millipedes,
insects, etc.
* Crustaceans mainly inhabit aquatic systems
* Insects dominate terrestrial environments
* Arthropod body
* Segmented body with jointed-appendages
attached (making antennae, pincers, legs, etc.)
* Pair of compound (multi-lens) eyes
* All body parts coated with cuticle, even the joints
* Moulting necessary for growth
* Very expensive and dangerous for the animal
* 'Soft shell crabs' are crabs which have just moulted
and has a soft-shell (it's not a specific species)
70
what makes insects unique with arthropods?
Enormous diversity
Often co-evolved with angiosperms (pollination mutualism)
Three body regions: head, thorax, post-genital
3 pairs of legs on thorax
Usually 1–2 pairs of wings, cuticle extensions, on dorsal thorax
71
what is metamorphosis?
📚 In simple terms:
Metamorphosis = Major change in body from youth → adult
🐛 Two main types in insects:
Incomplete Metamorphosis
Young = nymph
Nymph looks like a small version of the adult
Grows gradually through molting
Example: grasshoppers, dragonflies
Complete Metamorphosis
Young = larva (looks very different from adult)
Transforms into adult through a pupa stage
Example: butterflies, bees, beetles
72
what is incomplete metamorphosis?
Nymphs resemble miniature adults
Develop through gradual molts
Common in: grasshoppers, dragonflies, cockroaches, praying mantis, lice
Nymphs may lack wings and have different proportions
Dragonfly nymphs are aquatic with gills
🐞 What is Incomplete Metamorphosis?
Incomplete metamorphosis is a type of development in some insects where the young look like small versions of the adult, and they change gradually without a pupal stage.
🔄 3 Stages of Incomplete Metamorphosis:
Egg
Nymph – a smaller, immature version of the adult
Adult – fully developed, with wings (if the species has them) and reproductive organs
🟢 Key Points:
The nymph hatches from the egg and looks like a mini adult but usually lacks wings and reproductive organs.
It goes through several moults (shedding exoskeletons) as it grows.
With each moult, the nymph gets bigger and more like the adult.
No pupa/chrysalis stage (unlike in complete metamorphosis).
🐜 Examples of Insects with Incomplete Metamorphosis:
Grasshoppers
Crickets
Dragonflies
Cockroaches
🧠 Simple Summary:
Incomplete metamorphosis = gradual change from egg → nymph → adult, with no pupal stage and nymphs that look like young adults.
73
what is complete metamorphosis?
Life cycle: larva → pupa → adult
Larva: specialized for eating (e.g., caterpillars, maggots)
Adult: specialized for dispersal and reproduction
Example: butterflies, bees, beetles, flies
Pupa stage: larval tissues break down and adult is built anew
✅ Complete Metamorphosis
➡️ There is no nymph stage at all.
➡️ The young stage is called a larva, and it looks completely different from the adult.
➡️ It also goes through a pupa stage where it transforms.
🐛 Example (Butterfly):
Egg → Larva (caterpillar) → Pupa (chrysalis) → Adult (butterfly)
The caterpillar looks nothing like the butterfly.
74
what are dueterostomes and what are their major groups?
A major clade of animals within Bilateria
Named for their embryonic development (blastopore becomes anus)
Two main groups:
Echinoderms (e.g., sea stars, sea urchins — invertebrates)
Chordates (vertebrates like fish and mammals, and some invertebrates like lancelets and tunicates)
75
what are chordates and their four key derived traits
Members of Deuterostomia
with four derived traits
Notochord – flexible rod for skeletal support
Dorsal, hollow nerve cord – becomes brain and spinal cord
Pharyngeal slits/clefts – openings near pharynx, various functions
Muscular, post-anal tail – tail that extends beyond anus
76
what is the notochord and its function?
A flexible, longitudinal, rod-like structure between the digestive tube and nerve cord
Provides skeletal support
In vertebrates, it’s replaced by the backbone (vertebrae)
(in vertebrates the backbone develops around the embryonic notochord, in humans, it reduces, and beocmes part of the intervertral discs)
In humans, it becomes part of the intervertebral discs
In humans, the notochord starts off as a flexible rod in the embryo. As the spine forms, it mostly gets replaced by vertebrae, but some of it stays and becomes part of the intervertebral discs, which cushion your spine and help with movement.
77
what does it mean that the notochord is replaced by the backbone in ertrbrates
1. In early development:
All chordates (including humans) start with a notochord — a flexible rod that supports the embryo's body.
2. In vertebrates (like humans):
As the embryo grows, bones called vertebrae start to form around the notochord.
These bones become your spine (backbone).
3. So what happens to the notochord?
It gets mostly replaced by the vertebrae.
But a small part of it remains in humans — it becomes part of the intervertebral discs (the soft pads between the bones in your spine that act like shock absorbers).
78
what is the dorsal, hollow nerve cord and how does it form>
Develops from ectodermal tissue (neural plate) that folds/rolls and internalizes into a neural tube
Located dorsal (above) to the notochord
Develops into the brain and spinal cord
Contrast: other animals have solid, ventral nerve cord
79
what are pharyngeal slits or clefts in chordates?
pharynx: region just posterior to the mouth (towards back of mouth)
Appear in the region posterior to the mouth (pharynx)
pharyngeal clefs: chordate embryos has arches and grooves that forms along the outer surface of the pharynx
In some chordates:
Become open slits used for feeding or gas exchange (e.g., gills in fish)
In tetrapods (e.g., humans):
Do not become slits; instead, form face and neck structures
in humans, pharyngeal. clefts differentiate and form various muscle, nervous, and skelatal tissues around the face and neck.
80
what is the muscular post anal tail in chordates?
chordates have a muscular tail that Extends beyond the anus (in many spiecies, the tial is greatly reduced/lost during embryonic development)
Contains muscle and skeletal elements
Often used for movement
In humans and many other chordates, it's reduced or lost during development
81
what are lancelets and what chordate traits do they have?
Invertebrate chordates
Retain all 4 chordate traits as adults(notochord, dorsal, hollow nerve-cord, pharyngeal slits, and post anal tail)
Live buried in sand, use cilia around the mouth to filter feed (adult have it around their mouth and burrow their tail ends into sand and use cilia to draw water into their mouths to capture food)
No backbone, but a fully functional notochord and dorsal nerve cord
82
what are tunicates and what makes them unique?
More closely related to vertebrates
than lancelets
* Larvae resembles a 'normal’ Chordate
with all four Chordate traits
* Larvae settles at a suitable location and
goes under radical metamorphosis
* Notochord and tail resorbed
* Nervous system degenerates
* Filters water through the enlarged
pharynx-slits to get food
83
do all adult chordates retain the four traits?
No. Many lose some traits as adults
But all 4 traits are typically observed during embryonic development
84
how do humans show chordate traits during develpment?
Human embryo has all four
derived features of Chordates.
During development:
* Notochord gets replaced by the
vertebra
* Nerve chord develops into spinal
chord and the brain
* Pharyngeal slits develop into
various tissues of face and neck
* Post-anal tail recedes
85
how do adult chordates (lancelets, tunicates, humans) compare in the four derived traits?
Trait Comparison:
Notochord
→ Lancelets: Present
→ Tunicates (Adult): Absent
→ Humans (Adult): Reduced (in intervertebral discs)
Dorsal Nerve Cord
→ Lancelets: Present
→ Tunicates (Adult): Absent
→ Humans (Adult): Present (spinal cord)
Pharyngeal Slits
→ Lancelets: Present
→ Tunicates (Adult): Present (enlarged for filter feeding)
→ Humans (Adult): Absent (form parts of face/neck)
Post-anal Tail
→ Lancelets: Present
→ Tunicates (Adult): Absent
→ Humans (Adult): Absent (regresses in embryo)
86
waht defines vertebrates?
Animals with a skeletal system and a complex nervous system (better ability to chase pray and run from predator)
Most have vertebrae that enclose the spinal cord (replaces the mechanical roles of notochord)
early divereged
87
what are key features of early diverged vertrbrates like lampreys?
Early-diverged vertebra
* No jaws
* Cartilage skeleton, composed of
extracellular matrix proteins like collagen
* Cartilage can be mineralized with
calcium for added support
88
what are gnathostomes and what do they include?
Jaws: hinged structures that enable
animals to grip food items / slice them
* Cartilage fish (sharks, rays, etc.)
* One of the biggest and most successful
vertebrate predators in oceans
* Predominantly cartilage skeleton
* Limited use of mineralization may be a
'derived trait' for these species, as
mineralization was present before
they diverged from other vertebrates
89
what are the two groups of bony fish and how are they different?
Ray-finned fish:
→ Bony rays with webs, no muscle
→ Most common fish today
Lobe-finned fish:
→ Pectoral and pelvic fins have a thick muscle
supporting the bony fin
→ muscular funs can be used to “walk” on bottom of water
→ Includes coelacanths, lungfish, tetrapods
→ not too many extant species with some exception
90
what are the three groups of lobe finend fish?
Coelacanths – "living fossils," unchanged for ~400 million years
Lungfish – breathe using lungs + gills
Tetrapods – adapted to land, fins → limbs with digits (Muscular, pectoral and pelvic fins of lobe-fin
fishes evolved into limbs with digits)
91
what are tetrapods and what adaptations do they have?
"Four-limbed" vertebrates (Greek: "tetra" = four, "pod" = foot)
Limbs support body weight and help walk
Digits transmit force to ground
Includes amphibians, reptiles, mammals
92
what defines amphibians and their life cycle?
Salamanders, frogs, caecilians
Name means "both lives" (aquatic + terrestrial)
Tadpole: aquatic larva (gills, tail, legless, herbivore)
Adult: land-dweller (lungs, legs, no tail, carnivore)
Lay eggs in moist environments (eggs are not well protected from desiccation)
Use skin for gas exchange
93
what are amniotes and what makes their eggs special?
Amniotes are tetrapods with terrestrially
adapted eggs
* Reptiles and mammals
* Amniotic egg contains specialized
membranes to nurture the embryo
* Amnion is the membrane that encloses the
amniotic fluid which the embryo floats in
* Other membranes function in gas exchange,
transfer of nutrients, waste storage
* Amniotic egg allows terrestrial organisms
to nurture embryo without having access
to a body of water
94
what are the two thermal strategies in reptiles?
Ectothermic (e.g., lizards, snakes): use external heat
→ Require less energy (use 10th of tne energy to survive compared to a mammal of the same size)
Endothermic (birds): generate body heat via metabolism
→ High energy, survive cold (less energy efficient but resillient to harsher environments)
95
what makes mammals unique?
Mammals are Amniotes that have hair and
produce milk to nurture the young
* Milk: balanced diet rich in fats, sugars,
proteins, minerals and vitamins
* Produced in mammary glands
* Mammals are endothermic with high
metabolic rate
* Hair and fat layer under the skin provides
insulation
* Have a larger brain for body size
* Allows complex learning behavior such as
offspring learning skills from parents (knowledge
transfer, not just 'learning')
96
what are the three types of mammals?
Monotremes – egg-laying (platypus, echidna – Australia only)
Marsupials – develop in pouch (kangaroo, opossum)
Eutherians – placental mammals, full development in uterus
97
how are marsupials different from eutherians?
Marsupial: short pregnancy, nutured by placenta → young develops in pouch anddd most extant marsupials in the the australian region
(marsupials like opossum are the few marsupial species that still survive in north/central america)
Eutherian(placental mammals): longer pregnancy, complex placenta → full development in uterus anddd various life forms and habitats with a wide range of food, meat,nuts,grass,insects... teeth of mammals bear a variety of sizes and shape adapted for chewing many kinds of foods.
Convergent evolution: similar body forms in both due to shared niches
98
how is mammalian digestion adapted to diet?
Carnivores: short gut, large stomachs
Herbivores/Omnivores: long alimentary canals
→ Harder to digest cellulose
Ruminants (e.g., cows):
→ Host gut microbes to digest plant material
→ Regurgitate & re-chew food
→ Microbes convert cellulose → sugars
99
whats the digestive tract and adaptation of cows like?
Gut microbiome: we co-exist with
beneficial microbes living in our intestine
* Mutualistic gut microbiome is especially
important in herbivores
* Vertebrates can not digest cellulose cell wall
of plants to convert it to energy
* Many herbivores host various mutualistic
bacteria and protists in fermentation
chambers of their alimentary canals
* These microorganisms digest cellulose to
simple sugars that the animal can absorb
100
what are the three groups of primates?
Lemurs, lorises, bush babies
Tarsiers
Anthropoids – monkeys, apes
101
what key features define primates?
Opposable thumbs for grasping
Forward-facing eyes → depth perception
Large brain, flat face, short jaws
Strong parental care and social behavior
102
what are apes and how are they different from monkeys?
Larger body size
No tail
More advanced brains
Gibbons & orangutans = arboreal
Gorillas, chimps, humans = mostly terrestrial
Humans are the only bipedal apes
103
WHAT Are hominins?
:
Extinct species more closely related to humans than apes
First appeared ~6.5 million years ago
Bipedal locomotion (walking on two legs) was early trait
Multiple lineages existed, only Homo sapiens survived
use of tools may have evolved after bipedal locomotion
evidences show hominins cutting flesh from bones of animals and other nonhominin apes can use tools too like orangutans putting sticks into holes to fish food, etc
104
what do we know about neanderthals?
Lived ~400,000 to ~28,000 years ago
Used tools, hunted, buried dead
Not direct ancestors, but interbred with humans
Gene flow exists between Neanderthals and Homo sapiens
105
what defines homo sapiens?
Early Homo all spread from Africa into
Europe/Asian regions as they diversified
* Homo habilis, 2.4 – 1.6 million years ago
* Homo ergaster, 1.9 – 1.5 million years ago
Appeared ~200,000 years ago
Symbolic thought, language, tools
Artistic expression (e.g., cave paintings 30,000+ years old)
Shorter digestive tract, reduced jaws, jaw muscles
Cultural transmission (learning from others) language, symbolic thought, artistic expression, manufacture and use of complex tools
106
how does the cycle of life o earth involve plants, animals, bacteria, and energy flow?
Plants perform oxygenic photosynthesis
→ Use sunlight + CO₂ + H₂O to make sugars and release O₂
Cows (herbivores) eat plants
→ Use gut microbes to digest cellulose from plant cell walls
→ Produce milk as a food product
Humans consume plant-based foods and animal products (e.g., milk, yogurt)
→ Yogurt is made using Gram-positive bacteria via fermentation
→ Humans digest foods with help from mutualistic gut bacteria
→ Perform aerobic respiration: glucose + O₂ → energy + CO₂ + H₂O
