BSCI160 Exam 2

Haploids vs Diploids

Haploids have one of each chromosome, diploids have 2 of each chromosome

Asexual reproduction

offspring are clones of parents, no change in chromosome number

Why might organisms not do sexual reproduction?

its inefficient, costly, and risky for survival

Facultative sexual

Sometimes asexual, sometimes sexual

“The Tangled Bank Hypothesis” by G.Bell

Sexual reproduction is advantageous in complex environments with limited resources (differentiation increases survival rate)

“The Red Queen Hypothesis” L. Van Valen

Sex provides varied offspring allowing for rapid evolution

Conflict between the sexes

small male investment, large female investment, males compete, females choose, different traits between sexes

Sexual Selection

Differential success among individuals in acquiring mates (male competition and female choice)

Sexual dimorphism

Darwin- males and females differ through physical traits and aggressiveness

Intrasexual selection

Favors the evolution of mechanisms that enhance ability to compete with other members of one’s own sex

Female choice hypothesis - Why do females prefer a particular male trait?

Direct benefits, good genes, sexy sons/ runaway selection

Biological species concept (BSC)

all member have the potential to interbreed under natural conditions and produce viable, fertile offspring

Problems with BSC

subspecies, hybrids, doesn’t apply for asexual organisms, ring species

Prezygotic barriers

Separates species by preventing the formation of a zygote or fertilized egg(habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation)

Post-zygotic barriers

Separates species by preventing development of viable or fertile offspring (reduced hybrid viability, hybrid infertility, hybrid breakdown)

Allopatric Speciation

a mechanism of speciation, a physical barrier that divides the population

Sympatric Speciation

a mechanism of speciation, no physical barrier, but changes in behavioral traits

Autopolyploidy

duplication of chromosome number reproductively isolates offspring from parent population

Allopolyploidy

Hybridization and errors in meiosis lead to polyploid offspring with chromosomes from 2 different species (odd number)

Phylogeny/cladogram

a tree depicting different species and their ancestors, often showing shared traits

Phylogeny sister groups

two groups more closely related to each other than anything else on the tree

Phylogeny monophyletic group

includes a common ancestor and all of its descendants

Phylogeny paraphyletic group

includes a common ancestor and some but not all of its descendants

Phylogeny polyphyletic group

does not include the common ancestor

know how to build a phylogeny

:)

Phylogeny Synapomorphies

shared derived characteristics that are new and arose from a common ancestor

What is life?

Respond, grow, reproduce, heredity, homeostasis, metabolism, cellular

3 things that the earliest, simplest life needed to have

1. Use proteins for energy

2. ability to pass genetic information

3. cell with genetic info

Challenges in identifying the origin of life

can’t observe, complex forms, which came first DNA or proteins, only one earth

Signatures of life (what are we looking for to decide when life appeared?)

organic compounds, cold source, hot source (thermal vents), out of world source, microfossils, changes in rocks (carbon dating)

3 domains of life

Bacteria, Archaea, Eukarya (Eukaryotes)

What did the early life look like?

4.6-billion-year-old Earth was hot, barren, with low oxygen, over time it cooled, oceans formed

Development of new metabolic strategies

Photosynthesis —> cellular respiration —> endosymbiosis for chloroplasts and mitochondria (study again)

5 major changes + impacts

1. continental drift

2. climate change/sea level change

3. volcanic eruptions

4. meteorite strikes

5. atmospheric oxygen concentration

All eukaryotes have

an Archean cell as an ancestor

What are protists?

a catch-all category for things that act like animals but are usually unicellular, polyphyletic group, eat organic matter or do photosynthesis

Beneficial protists

phytoplankton, diatoms, dinoflagellates, brown algae,

Harmful protists

diatoms and dinoflagellate (in enormous numbers), plasmodium (causes malaria), giardia lamblia, disease protists

What is colonial multicellularity?

2+ individuals of the same species living in closer association with or connected to one another

What are the pros of being multicellular?

cells do different things, less risk of being eaten, more access to environment, longer lifespan, complex

What are the cons of being multicellular

more energy, slower reproduction, cooperation of cells, high risk high rewards

What are the properties of simple multicellular organisms?

adhesion molecules, all cells retain full range of functions, every cell in contact with external environment, lack of 3D structure

What are the rules for complex multicellularity?

cell communication, different types of tissues and organs, signal and sensory, regulatory genes mapping the body

Land plants

come back to this

What are fungi?

Monophyletic, decomposers (dead material and food), pathogens, mutualists, complex

What is fungi yeast?

not a monophyletic group, single celled, grow by budding, refers to different species, can be haploid, diploid, or dikaryotic

What is fungi hyphae?

multi-cellular branching growth (average mushroom), parasitic fungi

What are animals?

monophyletic group, multicellular, heterotrophic metabolism, internal digestion, movement, nervous systems, segmentation, appendages

What is gastrulation in animals?

the zygote first dives into a blastula (hollow ball of cells) then infolds to create distinct tissue layers

Where did the nervous system evolve?

triploblastic animals (bilaterians)

What are sponges?

can move, filter feeders, no nervous system, no distinct tissue layer,

What are cnidarians?

move with simple muscles, some capture prey, some filter feed, nerve nates, 2 tissue layers, asymmetric (jellyfish, corals, etc)

What are the two branches in the bilaterian tree?

protostomes (mouth forms first then anus) and deuterostomes (anus forms then mouth)

What are echinoderms?

loss of head, simple nervous system, change in symmetry and appearance

What are arthropods?

jointed appendages, regional segmentation, exoskeleton, open circulatory system, diverse