Plants + Animals (Day 1-3)

Plants benefit on being underwater

• Buoyancy

• Bathed in nutrients

• Extensive transport not necessary

• Gametes + offspring can be dispersed via water current

• No problem of desiccation (drying out)

Plants benefit of living on land

• More direct sun (enough ozone to filter harmful UV radiation)

• Untapped nutrients and minerals on land

• Abundant CO2 for photosynthesis

• Initially, an absence of herbivores

• New niches opening up to colonize

Dispersal

For plants, movement of seeds or spores away from parent plant to a new location (reduces competition and increases survival), allows for reproduction

Dispersal strategies

• Wind

• Ballistic/explosive

• Water/floating

• Gravity/rolling

• Movement by animals (attached or excreted)

Key plant features from ancestors

• Photosynthetic pigments (chlorophylls)

• Cell walls (made of cellulose)

• Sperm w/ tails (flagella)

New features in land plants

• Cuticle (waxy layer) to prevent water loss

• Alternation of Generations defined by NEW multicellular diploid stage

Alternation of Generations

Generations switch from having a diploid life cycle to a haploid life cycle

Haploid Life Cycle

Diploid zygote fertilized by putting 2 haploid gametes together. Then, after splitting through meiosis, spends most of its life as a haploid doing mitosis to become grown multicellular individuals/multiple cells

Diploid life cycle

Haploid gametes fertilize to become diploid zygote. Zygote goes through mitosis to become a grown individual. Once a grown individual, does mitosis to create the gametes

Alternation of Generations Life Cycle

Haploid cycle begins when spores do mitosis to become multiple cells then 2 gametes fuse. Once fused, diploid cycle starts and zygote goes through mitosis then the grown individual does meiosis to create spores, ultimately causing the haploid cycle to start again

Gametophyte

The haploid life cycle’s multiple cells, makes gametes (mitosis), grows from a gamete (then does mitosis), is haploid.

Sporophyte

The diploid life cycle’s grown individual, makes spores (meiosis), grows from a zygote (mitosis), is diploid

Adaptive Radiation

Population of one species disperses throughout an area, each finding a distinct role, food, source, habitat. Many adaptions from one starting point

Nonvascular Plants

Type of adaptive radiation. New innovations are live on land, cuticle, and alternation of generations. Relies on water for reproduction bc lets sperm swim thru water to eggs. Gametophyte is dominant stage. Spores fall from capsule at top of sporophyte and move via wind and gravity to disperse.

Seedless Vascular Plants

Adaptive radiation. New innovations are vascular tissue (large size so support against gravity and efficient distribution of water and nutrients) and leaves (flat surfaces for photosynthesis). Relies on water for reproduction bc lets sperm swim thru water to eggs. Sporophyte is dominant but gametophyte is semi-independent. To disperse, spores often explode and/or via wind and gravity

Gymnosperms (naked seed plants)

Adaptive radiation. New innovations are seeds and pollen. Water isn’t required to reproduce, instead use pollen. Dominant stage is sporophyte. Pollen moves via wind, seeds move via animals/wind/gravity. “Naked seed” = No ovaries for development of seeds.

Angiosperms

Adaptive radiation. New innovation in the group are flowers (uses animals to pollinate and more efficient pollination as they don’t rely on wind, avoids inbreeding, can reproduce even when low abundance) and fruit (great for dispersal). Water isn’t required to reproduce, instead use pollen. Dominant stage is sporophyte. Pollen moves via wind, seeds move via animals/wind/gravity.

Animals

Ingestive heterotrophs with no cell walls

General characteristics of animals

• Multicellular

• Heterotrophic metabolism (need to eat to get nutrients)

• Internal digestion (inside the body)

• Movement (at least part of the lifecycle)

• Nervous systems (many, but not all)

Where did animals come from?

A monophyletic group with origins among the “protists”. Evolved multicellularity independently of plants, fungi.

Body plan

General structure, arrangement of organ systems, and integrated functioning of body parts

Four key features of the body plan

Types of symmetry + number of tissue layers, segmentation present or not, external appendages present or not and what do they look like, nervous system present or not and how complex

Where does symmetry + number of tissue layers come from and how?

Early division of the zygote. Zygote divides into a blastula which then does gastrulation

Blastula

A hollow ball of cells

Gastrulation

Infolding of the blastula to create distinct tissue layers. Can decide what type of animal is formed. (Make sure to study process)

What three layers can form during gastrulation

Endoderm, mesoderm, ectoderm

Endoderm

Inside, the gut

Mesoderm

Middle, muscles + organs

Ectoderm

Outside, skin + more

True tissue

Tightly connected layer of cells that work together for a specific function. A few interspersed cells types aren’t this. Examples are muscle tissue, nervous tissue, connective tissue.

Asymmetry

No plane of symmetry, 0 tissue layers

Radial symmetry

2 tissue layers, body parts arranged around a central axis

Bilateral symmetry

3 tissue layers, can be divided into mirror image halves on only one plane

Cephalization

Development of head, sensory organs in front of it, often a brain to interpret and respond to signals

Correlation between bilateral and cephalization

Bilateral symmetry creates a distinct front (anterior) and back (posterior), as well as left and right sides. Because a bilaterally symmetrical animal moves forward through its environment in a directional way, the anterior end is always the first part of the body to encounter food, shelter, or danger.

Segmentation

Facilitates specialization of body regions

Segmentation uses and importance

Allows an animal to alter their body shape and control movements precisely, all mammals

Appendages

Enhance an animal’s ability to move around, feed, smell/taste, reproduce

Appendages examples

Antennae, claws, mouthparts, and reproductive organs

Nerve nets

Type of nervous system, diffuse (basically unorganized) nervous systems in early animals, likely a result of convergent evolution

Central nervous systems

Type of nervous system, bilaterians have this, muscle action is coordinated to allow movement of appendages and body parts, sensory info is gathered and processed

Where did the nervous system types evolve?

Around the split in the phylogeny that leads to the bilaterians and cnidarians

Sea sponges

• Can move but must leave parts of body behind

• Are filter feeders (filter nutrients/food from water by creating a current to pull) so no true stomach

• Have no nervous system at all

Cnidarians

• Can move with simple muscles

• Some capture prey, some are filter feeders

• Have a nerve net and some have simple eyes

• Have 2 tissue layers and are radially symmetric

• Have a stomach but only one opening

• Jellyfish + relatives

Bilaterians

• 2 openings

• Food tube from the mouth to anus

Two Great Branches of Bilaterian Tree

Protostomes (form mouth first) and deuterostomes (form anus first).

Does protostomes vs. deuterostomes really matter later in life?

Not really. However, Protostomes nerve chords are ventral while in deuterostomes are dorsal

Lophotrochozoans

Segmented bodies (like worms and mollusks), some with advanced nervous systems

Ecdysozoans

Molt and shed an exoskeleton (ex: nematodes, crabs, insects, etc.)

Arthropods

Type of ecdyszoa, exoskeleton (chitin), jointed appendages, segmentation, huge species diversity

Insects

A type of ecdyszoa and arthropod, most diverse group of animals (over 1 mil described species but most likely 5-10 mil/many more). Reasons for large diversity are modifiable exoskeleton, wings, small size, fast reproduction

Echinoderm

Loss of head, simple nervous system, change in symmetry + appearance (ex: sea stars)

Chordates

Segmentation, dorsal notochord and nerve cord later replaced by spine and spinal cord in some groups. Mostly made of vertebrates.

How to differentiate an insect from fish

Insects (protostomes) have nerve cord along belly while fish (deuterostomes) have it along the top/back (in a notochord)

Vertebrates

• Type of chordate

• Jointed, dorsal vertebral column (rigid internal skeleton support by vertebral column and integrated w/ spinal cord)

• skull with large brain and developed sensory organs

• well-developed circulatory system with a ventral heart

• internal skeleton gives support for muscular system, allowing them to become large predators and diversify widely

Sequential adaption to land by vertebrates

• Jawless vertebrates

• Jaw evolution

• Cartilaginous skeletons

• Bony fish

• Colonization of land

• Evolution of tetrapods

• Amphibians

• Amniotes

Jawless vertebrates

• Hagfish: Most primitive living vertebrate, have a skull but no true spine so only sometimes placed in this group

• Lampreys: Predatory parasites

• Both eat through pinching their teeth onto prey

Jaw evolution

• Evolve from gill arches

• More effective feeding

• Supports higher metabolism

Cartilaginous skeletons

• Are lighter and more flexible but not as strong as bone

• Sharks and rays: jaws but no bone

Bony fishes

• Calcified bone skeleton instead of cartilage

• 3 groups: ray-finned fishes (99% of fish species), lobe-finned fishes, lungfishes (gills and lungs)

The colonization of land + tetrapods

• To live on land as a vertebrate you needed lungs, legs, and water tight skin in order to not desiccate (dry out)

• Tetrapods = four-legged vertebrates

• Earliest tetrapods limbs may have held animals upright enough in shallow water to be above the water

• Limbs eventually co-opted for movement on land

• Jointed appendages (allow more effective movement)

• Amphibians, reptiles, birds, mammals

Amphibians

• Frogs, salamanders, caecilians

• Not fully terrestrial as adults need to stay moist to avoid desiccation, eggs need to be laid in water, babies are completely aquatic

Amniotes

• Reptiles, mammals

• Dry scaly skin to prevent desiccation, reduce water loss, to live in dry conditions. Similar to plant cuticle

• Excretory organs: allowed storage and excretion of concentrated urine. Excreted nitrogenous waste w/o losing water

• Amniotic egg: Thick shelled egg that prevent desiccation of embryo, allows reproduction on land

Amniotic egg parts

• Shell: protects embryo from environment

• Allantois: storage of wastes, in amnion

• Chorion: right under shell and contains amnion, allows for gas exchange

• Yolk sac: In amnion, food

Mammalian/mammal traits

• Hair

• Lactation

• Sweat glands

Prototherians vs Therians

Lays eggs vs. live birth (viviparous) and has 2 types

Marsupials

offspring birthed early in development, carried and fed in a central pouch

Eutherians

offspring birthed later in development, the majority of mammals

Cetaceans (whales, dolphins, narwhal)

Example that shows mammals went back into aquatic habitats

Primates

• Evolved from a lineage of small, arboreal, insectivorous eutherians

• 35 mya: Ape lineage separated from Old World monkeys

• 6 mya in Africa: Ancestral split that eventually led to the chimpanzees and humans