Animal Digestive and Respiratory Systems
Stomach
The stomach is a dilated section of the digestive tract that stores food temporarily before it moves to the intestine in a more broken-down state.
Stomach Variations in Vertebrates
- Fish, Amphibians, and Reptiles: Spindle-shaped stomach.
- Birds: Divided into a muscular gizzard, specializing in food trituration, and a glandular section.
- Mammals: Highly folded stomach structure.
- Ruminant Mammals: Complex stomach divided into four chambers: rumen, reticulum, omasum, and abomasum. Unchewed grass is
Nervous and Endocrine Systems: Cells, Hormones, and Plant Responses
Neurons and the Nervous System
Neurons are specialized cells that transmit nervous impulses. Their filamentous structure, with characteristic extensions, allows them to connect to other neurons or organs. The extensions of neurons form fibers, which are grouped into bundles. Several of these bundles, in turn, form nerves.
Neuron Structure
- Cell body: Contains the nucleus and part of the cytoplasm.
- Axon: A long extension, branched at its end, that conducts the nerve impulse to another neuron or organ.
Cell Theory: Prokaryotic and Eukaryotic Cells
Principles of Cell Theory
- Cells are the basic unit of living things.
- Every cell comes from another cell.
- Preexisting cells transmit information from one generation to another.
Prokaryotic Cells
Unicellular, prokaryotic DNA is dispersed in the cytoplasm. They have no organelles except for ribosomes, a cell wall, and a plasma membrane that folds. Some have flagella.
Structures:
- Plasma membrane
- Ribosomal DNA
- Cell wall
- Cytoplasm
- Flagella
Eukaryotic Cells
Eukaryotic cells can be unicellular or multicellular. They
Read MoreHomeostasis, Osmoregulation, Growth, and Reproduction in Organisms
Homeostasis
Homeostasis is the maintenance of relatively stable internal conditions despite changes in the external environment. In humans, the hypothalamus checks the current temperature to match the normal 37°C.
Enzyme Activity
For every 10°C rise in temperature, enzyme activity doubles.
Heat Exchange Equation
Hs = Hm + Hcd + Hcv + Hr – He
- s (stored heat in the body)
- m (metabolism)
- cd (conduction)
- cv (convection)
- r (radiation)
- e (evaporation)
Variation in Body Temperature
- Poikilotherms: Body temperature
Natural Selection and the Evolution of Species
**Natural Selection**
- Over time, populations with traits less suited to the environment will decrease.
- Organisms best adapted to their environment will thrive.
- Giraffe Example: Giraffes with longer necks can reach higher leaves, giving them an advantage.
- Accumulated changes over generations can lead to the formation of new species.
**Neo-Darwinism – Synthetic Theory**
Neo-Darwinism rejects Lamarckism. The unit of evolution is the population, not individuals. Genetic mutations and natural selection drive
Read MoreGenetic Concepts and DNA Technology: A Comprehensive Overview
Key Genetic Terms and Concepts
Locus: The physical location of a gene on a chromosome.
Allele: Different versions of a given gene. New alleles form because of mutations, changes in the DNA. Mutations can be:
- Neutral (most of the time)
- Harmful (sometimes)
- Beneficial (occasionally)
Genotype: The combination of alleles an organism has.
Phenotype: The combination of alleles that create a physical trait.
Homozygous: If the alleles at a given locus are the same.
Heterozygous: If the alleles at a given locus are
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