Class notes
Biol 114 Animal Form and Function Notes
- Course
- Biology 114
- Institution
- State University Of New York - Binghamton
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Biol. 114 Spring 2021Lecture week 8
Animal Form and Function
I. Introduction
A. Limits and tradeoffs
Giant fire-breathing monsters with extra limbs, bugs the size of skyscrapers, giant squids that
can walk around on land – they would probably have a pretty easy time surviving. So why don’t
they exist?
Evolution can only work through mutations and standing genetic variations (can’t invent
something completely new)
1. Designs have plasticity (flexibility) within certain limits. Plasticity is the ability
for trait to change based on environmental conditions (not talking about genetic
change/evolution).
a) Amphibians like frogs and toads grow throughout their whole lives. The rate
at which they grow is dependent upon many factors including resource
availability and space. However, even with infinite resources, time, and
space, a frog could only ever get to be about the size of a dinner plate. This is
because they have no supporting structures on their ventral side. If they were
to become too large, they could not support their own internal organs.
2. There’s never just one selective pressure; as you get better at one thing, you often
have to sacrifice something else. Everything (survival) is based on compromise….
Trade-offs necessary
a) Example: Giraffes have very long legs and necks which help them reach the
tops of trees, avoid predation, and large necks are selected for in males to win
fights against other males. However, these long necks require specialized
vein systems in order to keep them alive while they drink, and even so they
have to put themselves in an extremely vulnerable position to do so. Large
males will often get on their knees in order to drink, making it much harder to
get away should a predator approach.
b) Environmental variability: Different environments demand different suites
of adaptations, e.g. an animal can’t master terrestrial life without
compromising aquatic life. A hippo is a comparatively slow swimmer
compared to a killer whale, but much more versatile on land.
c) Becoming larger to escape predation or to increase one’s competitive edge
against other species requires multicellularity, cell specialization, and organ
systems for transporting nutrients, water, energy sources and waste products
between the outer and inner environment of the organism.
II. Energy (has to get it, keep it, and use it)
1
, - Food
- Water
- Respiration
- Thermoregulation
A. Obtaining energy
1. For animals this means eating, but there are many different things out there to eat as
well as ways of getting them and converting them into energy. TRADEOFFS
(generalist or specialist? Eat plants, animals, or both?)
a) Generalists vs. Specialists: A generalist is good in everything, master of
nothing. There are advantages to both, but few organisms can shift between
being an effective generalist or specialist.
- Cost of being a generalist: under constant competition for food; one of
food sources may evolve a defense mechanism… benefit is that so
generalized, easier to find food
- Cost of being a specialist: if something happens to the one type of food
you go after (e.g., disease, extinction, defense mechanism), benefit is
competition is rare
(1) Example: Corvids such as the jungle crow are opportunistic
omnivores capable of eating a wide range of foods including fruits,
insects, and human garbage. As such, they are widespread and can be
found in most habitats across the globe, except for South America.
Hummingbirds, like the sparkling violetear, live exclusively in North
and South America and almost entirely in the tropics, with many
being endemic to only small and very specific habitats.
Hummingbirds are known for their unique bills which mirror the
flowers from which they get their food. As a result, hummingbirds
rarely have to compete for nectar with other animals because they are
specifically suited to their local flowers. Even within hummingbirds,
some species specialize in specific flowers that only they can get
nectar from. Crows are in constant competition with other animals,
many of which are better at getting specific food items than they are,
but since they have so many options they can always find something
to eat.
b) Herbivores, Omnivores (will be ok at eating both), and Carnivores
(1) Energy source variability: Different energy sources demand
different, mostly incompatible adaptations to access them, e.g.
evolutionary designs of plants vs. animals: no animal is able to
photosynthesize, and no plants eat other organisms. Carnivorous
plants kill insects but do so for a nitrogen supplement rather than a
calorie source. Plants have systems for accessing the glucose from
photosynthesis, but they have no mechanism for eating and internally
digesting other organisms to obtain glucose. Another example: a lion
can’t digest, much less chew, grasses like a cow (the interlocking
2
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